Fix MODULE_NOT_FOUND

By default the working directory of the composite action is the calling
workflows's context. This means a relative require like what was done here
isn't reading the action's main.yml.

This wasn't caught during testing because GHA requires one to check the testing
repo out before being able to run a local action. This masked the behavior.

I believe it was missed in the integration tests because those were tested when
the main.js was _embedded_ in the action.yml. Hilarious.

Author: dekimsey

action.yml

@@ -45,7 +45,7 @@ runs:
       with:
         # github-token: uncomment-this-line-for-local-act-testing
         script: |
-          return require('./main.js')({context, core})
+          return require(process.env.GITHUB_ACTION_PATH + '/main.js')({context, core})
     - name: Send Status
       uses: slackapi/slack-github-action@007b2c3c751a190b6f0f040e47ed024deaa72844 # v1.23.0
       env: