Hello! I added documentation for the GITHUB_ACTION_PATH env var that wasn't documented here. I copied the description from https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#github-context with a light edit to indicate we're talking about a variable and not an attribute.

Why:

Closes #5876

What's being changed:

Added Line 61

| `GITHUB_ACTION_PATH` | The path where your action is located. You can use this path to easily access files located in the same repository as your action. This variable is only supported in composite run steps actions. |

Check off the following:

• I have reviewed my changes in staging. (look for the deploy-to-heroku link in your pull request, then click View deployment)
• For content changes, I have reviewed the localization checklist
• For content changes, I have reviewed the Content style guide for GitHub Docs.