Fix MODULE_NOT_FOUND (#5)

* 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.

* Add an on-merge test case

Author: dekimsey

.github/workflows/test-integration.yml

@@ -0,0 +1,26 @@
+# Copyright (c) HashiCorp, Inc.
+# SPDX-License-Identifier: MPL-2.0
+
+name: test main integration
+# This workflow validates the merged code functions exactly as an invoking workflow might use it.
+# Due to the requiremnet that `uses` be a hard-coded value, we can only validate explicit git refs.
+# In this case, we validate once a PR has been merged, main branch functions correctly
+
+on:
+  pull_request:
+    types: [closed]
+
+permissions:
+  contents: read
+
+jobs:
+  main-merge:
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.merged == true
+    steps:
+      - uses: hashicorp/action-slack-status@main
+        with:
+          success-message: "Merge successfull"
+          status: ${{job.status
+          slack-webhook-url: ${{secrets.slack_webhook_url_feed_releng_test}}
+

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: