add usage to readme

README.md

@@ -14,7 +14,32 @@
 $ npm i -g updates
 ```
 
+# Usage
+```
+usage: updates [options]
+
+  Options:
+    -u, --update             Update package.json
+    -p, --prerelease         Consider prerelease versions
+    -j, --json               Output a JSON object
+    -g, --greatest           Prefer greatest over latest version
+    -i, --include <pkg,...>  Only include given packages
+    -e, --exclude <pkg,...>  Exclude given packages
+    -r, --registry <url>     Use a custom registry
+    -f, --file <path>        Use specified package.json file
+    -c, --color              Force-enable color output
+    -n, --no-color           Disable color output
+    -v, --version            Print the version
+    -h, --help               Print this help
+
+  Examples:
+    $ updates
+    $ updates -u
+    $ updates -u -e semver
+``
+
 ## Examples
+
 ### Check for updates
 ```console
 $ updates