feat/markdownlint (#200)

Hi,
this patch contains a markdownlinter. I think this has the advantage that all users stick to the same format and the `README.md` follows a consistent structure.

The markdownlinter can be configured via the `.markdownlint.yaml` file. All possible options are [here](https://github.com/DavidAnson/markdownlint/blob/main/schema/.markdownlint.yaml) documented.

I have created the initialie configuration. However, can be adapted to suggestions for change. Has of course the consequence that if necessary the `README.md` would have to be adapted. I have formatted this in advance according to the defined rules.

For users which use visual-code as IDE is additionally a plugin [available](https://marketplace.visualstudio.com/items?itemName=DavidAnson.vscode-markdownlint).

Co-authored-by: Markus Pesch <markus.pesch@cryptic.systems>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/200
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: pat-s <pat-s@noreply.gitea.io>
Co-authored-by: Markus Pesch <volker.raschek@noreply.gitea.io>
Co-committed-by: Markus Pesch <volker.raschek@noreply.gitea.io>

.drone.yml

@@ -1,5 +1,6 @@
 ---
 kind: pipeline
+type: docker
 name: lint
 
 platform:
@@ -7,12 +8,18 @@ platform:
   arch: arm64
 
 steps:
-- name: lint
+- name: helm lint
   pull: always
   image: alpine:3.13
   commands:
-    - apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/testing helm
-    - helm lint
+  - apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/testing helm
+  - helm lint
+
+- name: markdown lint
+  pull: always
+  image: docker.io/volkerraschek/markdownlint:latest
+  commands:
+  - markdownlint *.md
 
 - name: discord
   pull: always
@@ -29,6 +36,7 @@ steps:
 
 ---
 kind: pipeline
+type: docker
 name: release-version
 
 platform:
@@ -37,33 +45,33 @@ platform:
 
 trigger:
   event:
-    - tag
+  - tag
 
 steps:
-  - name: generate-chart
-    pull: always
-    image: alpine:3.13
-    commands:
-      - apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/testing helm
-      - apk add --no-cache curl
-      - helm dependency update
-      - helm package --version "${DRONE_TAG##v}" ./
-      - mkdir gitea
-      - mv gitea*.tgz gitea/
-      - curl -L -o gitea/index.yaml https://dl.gitea.io/charts/index.yaml
-      - helm repo index gitea/ --url https://dl.gitea.io/charts --merge gitea/index.yaml
+- name: generate-chart
+  pull: always
+  image: alpine:3.13
+  commands:
+    - apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/testing helm
+    - apk add --no-cache curl
+    - helm dependency update
+    - helm package --version "${DRONE_TAG##v}" ./
+    - mkdir gitea
+    - mv gitea*.tgz gitea/
+    - curl -L -o gitea/index.yaml https://dl.gitea.io/charts/index.yaml
+    - helm repo index gitea/ --url https://dl.gitea.io/charts --merge gitea/index.yaml
 
-  - name: upload-chart
-    pull: always
-    image: plugins/s3:latest
-    settings:
-      bucket: gitea-artifacts
-      endpoint: https://storage.gitea.io
-      path_style: true
-      access_key:
-        from_secret: aws_access_key_id
-      secret_key:
-        from_secret: aws_secret_access_key
-      source: gitea/*
-      target: /charts
-      strip_prefix: gitea/
+- name: upload-chart
+  pull: always
+  image: plugins/s3:latest
+  settings:
+    bucket: gitea-artifacts
+    endpoint: https://storage.gitea.io
+    path_style: true
+    access_key:
+      from_secret: aws_access_key_id
+    secret_key:
+      from_secret: aws_secret_access_key
+    source: gitea/*
+    target: /charts
+    strip_prefix: gitea/

.markdownlint.yaml

@@ -0,0 +1,149 @@
+# markdownlint YAML configuration
+# https://github.com/DavidAnson/markdownlint/blob/main/schema/.markdownlint.yaml
+
+# Default state for all rules
+default: true
+
+# Path to configuration file to extend
+extends: null
+
+# MD003/heading-style/header-style - Heading style
+MD003:
+  # Heading style
+  style: "atx"
+
+# MD004/ul-style - Unordered list style
+MD004:
+  style: "dash"
+
+# MD007/ul-indent - Unordered list indentation
+MD007:
+  # Spaces for indent
+  indent: 2
+  # Whether to indent the first level of the list
+  start_indented: false
+
+# MD009/no-trailing-spaces - Trailing spaces
+MD009:
+  # Spaces for line break
+  br_spaces: 2
+  # Allow spaces for empty lines in list items
+  list_item_empty_lines: false
+  # Include unnecessary breaks
+  strict: false
+
+# MD010/no-hard-tabs - Hard tabs
+MD010:
+  # Include code blocks
+  code_blocks: true
+
+# MD012/no-multiple-blanks - Multiple consecutive blank lines
+MD012:
+  # Consecutive blank lines
+  maximum: 1
+
+# MD013/line-length - Line length
+MD013:
+  # Number of characters
+  line_length: 80
+  # Number of characters for headings
+  heading_line_length: 80
+  # Number of characters for code blocks
+  code_block_line_length: 80
+  # Include code blocks
+  code_blocks: false
+  # Include tables
+  tables: false
+  # Include headings
+  headings: true
+  # Include headings
+  headers: true
+  # Strict length checking
+  strict: false
+  # Stern length checking
+  stern: false
+
+# MD022/blanks-around-headings/blanks-around-headers - Headings should be surrounded by blank lines
+MD022:
+  # Blank lines above heading
+  lines_above: 1
+  # Blank lines below heading
+  lines_below: 1
+
+# MD024/no-duplicate-heading/no-duplicate-header - Multiple headings with the same content
+MD024:
+  # Only check sibling headings
+  allow_different_nesting: true
+
+# MD025/single-title/single-h1 - Multiple top-level headings in the same document
+MD025:
+  # Heading level
+  level: 1
+  # RegExp for matching title in front matter
+  front_matter_title: "^\\s*title\\s*[:=]"
+
+# MD026/no-trailing-punctuation - Trailing punctuation in heading
+MD026:
+  # Punctuation characters
+  punctuation: ".,;:!。，；：！"
+
+# MD029/ol-prefix - Ordered list item prefix
+MD029:
+  # List style
+  style: "one_or_ordered"
+
+# MD030/list-marker-space - Spaces after list markers
+MD030:
+  # Spaces for single-line unordered list items
+  ul_single: 1
+  # Spaces for single-line ordered list items
+  ol_single: 1
+  # Spaces for multi-line unordered list items
+  ul_multi: 1
+  # Spaces for multi-line ordered list items
+  ol_multi: 1
+
+# MD033/no-inline-html - Inline HTML
+MD033:
+  # Allowed elements
+  allowed_elements: []
+
+# MD035/hr-style - Horizontal rule style
+MD035:
+  # Horizontal rule style
+  style: "---"
+
+# MD036/no-emphasis-as-heading/no-emphasis-as-header - Emphasis used instead of a heading
+MD036:
+  # Punctuation characters
+  punctuation: ".,;:!?。，；：！？"
+
+# MD041/first-line-heading/first-line-h1 - First line in a file should be a top-level heading
+MD041:
+  # Heading level
+  level: 1
+  # RegExp for matching title in front matter
+  front_matter_title: "^\\s*title\\s*[:=]"
+
+# MD044/proper-names - Proper names should have the correct capitalization
+MD044:
+  # List of proper names
+  names:
+  - Gitea
+  - PostgreSQL
+  - MariaDB
+  - MySQL
+  - Memcached
+  - Prometheus
+  # Include code blocks
+  code_blocks: false
+
+# MD046/code-block-style - Code block style
+MD046:
+  # Block style
+  style: "fenced"
+
+# MD048/code-fence-style - Code fence style
+MD048:
+  # Code fence syle
+  style: "backtick"