docs: Update the README for the cli for BEM conversion.

Author: chriseppstein

packages/@css-blocks/cli/README.md

@@ -15,19 +15,26 @@ or run without installation:
 npx @css-blocks/cli validate blocks/*.block.css
 ```
 
+```
+npx @css-blocks/cli convert my-bem-file.css
+```
+
 ## Usage
 
 ```
 css-blocks <cmd> [options] block-dir-or-file...
 
 Commands:
   css-blocks validate <blocks..>  Validate block file syntax.
+  css-blocks convert <files..>    Convert BEM syntax to block file syntax.
 
 Options:
-  --version        Show version number
-  --preprocessors  A JS file that exports an object that maps extensions to a preprocessor function for that type.
-  --npm            Allow importing from node_modules
-  --alias          Define an import alias. Requires two arguments: an alias and a directory.
-  --help           Show help
+  --version        Show version number                                [boolean]
+  --preprocessors  A JS file that exports an object that maps          [string]
+                   extensions to a preprocessor function for that type.
+  --npm            Allow importing from node_modules                  [boolean]
+  --alias          Define an import alias. Requires two arguments:      [array]
+                   an alias and a directory.
+  --help           Show help                                          [boolean]
 
 ```