Update yarn.py (#66973)

##### SUMMARY
To globally install from local node.js library. Prepend "file:" to the path of the node.js library.


##### ISSUE TYPE
- Docs Pull Request

+label: docsite_pr

lib/ansible/modules/packaging/language/yarn.py

@@ -29,6 +29,7 @@ options:
     description:
       - The name of a node.js library to install
       - If omitted all packages in package.json are installed.
+      - To globally install from local node.js library. Prepend "file:" to the path of the node.js library.
     required: false
   path:
     description: