feat(lang): add OCaml (#4079)

## Description

<!-- Describe the big picture of your changes to communicate to the
maintainers
  why we should accept this pull request. -->

Adds an extra that adds language support for ocaml.

Adds LSP and completions. Fairly simple/small config.

## Related Issue(s)

<!--
  If this PR fixes any issues, please link to the issue here.
  - Fixes #<issue_number>
-->

None

## Screenshots

<!-- Add screenshots of the changes if applicable. -->

<img width="1510" alt="lsp ocaml"
src="https://github.com/user-attachments/assets/0e44c539-332c-415d-9225-bcbb61f37666">


## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/plugins/extras/lang/ocaml.lua

@@ -0,0 +1,39 @@
+return {
+  recommended = function()
+    return LazyVim.extras.wants({
+      ft = { "ml", "mli", "cmi", "cmo", "cmx", "cma", "cmxa", "cmxs", "cmt", "cmti", "opam" },
+      root = { "merlin.opam", "dune-project" },
+    })
+  end,
+  {
+    "nvim-treesitter/nvim-treesitter",
+    opts = function(_, opts)
+      if type(opts.ensure_installed) == "table" then
+        vim.list_extend(opts.ensure_installed, { "ocaml" })
+      end
+    end,
+  },
+  {
+    "neovim/nvim-lspconfig",
+    opts = {
+      servers = {
+        ocamllsp = {
+          get_language_id = function(_, ftype)
+            return language_id_of[ftype]
+          end,
+          root_dir = function(fname)
+            return require("lspconfig.util").root_pattern(
+              "*.opam",
+              "esy.json",
+              "package.json",
+              ".git",
+              "dune-project",
+              "dune-workspace",
+              "*.ml"
+            )(fname)
+          end,
+        },
+      },
+    },
+  },
+}