Add @github/local-action and documentation

README.md

@@ -128,6 +128,34 @@ So, what are you waiting for? Go ahead and start customizing your action!
    > `ncc`, which will create a license file for all of the production node
    > modules used in your project.
 
+1. (Optional) Test your action locally
+
+   The [`@github/local-action`](https://github.com/github/local-action) utility
+   can be used to test your action locally. It is a simple command-line tool
+   that "stubs" (or simulates) the GitHub Actions Toolkit. This way, you can run
+   your JavaScript action locally without having to commit and push your changes
+   to a repository.
+
+   The `local-action` utility can be run in the following ways:
+
+   - Visual Studio Code Debugger
+
+     Make sure to review and, if needed, update
+     [`.vscode/launch.json`](./.vscode/launch.json)
+
+   - Terminal/Command Prompt
+
+     ```bash
+     # npx local action <action-yaml-path> <entrypoint> <dotenv-file>
+     npx local-action . src/main.js .env
+     ```
+
+   You can provide a `.env` file to the `local-action` CLI to set environment
+   variables used by the GitHub Actions Toolkit. For example, setting inputs and
+   event payload data used by your action. For more information, see the example
+   file, [`.env.example`](./.env.example), and the
+   [GitHub Actions Documentation](https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables).
+
 1. Commit your changes
 
    ```bash