MDBF-801: Add github status link to full Buildbot results

This enable users that submit pull requests to be able
to easily see the link to the full test results of
BuildBot.

Author: grooverdan

.github/workflows/autocomment.yml

@@ -0,0 +1,18 @@
+name: Check BuildBot
+
+on:
+  pull_request:
+    types:
+      - opened
+
+jobs:
+  auto-comment:
+    runs-on: ubuntu-22.04
+    steps:
+      - name: PR Comment
+        run: |
+          gh pr comment $PRNUM --body "Hi ${{ github.event.pull_request.user.login }}, some Buildbot tests are recorded as GitHub status builder here, however for the complete list of test results see this [BuildBot URL specific to this PR](https://buildbot.mariadb.org/#/grid?branch=refs/pull/${PRNUM}/head). The most recent push to this pull request is on the left."
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_REPO: ${{ github.repository }}
+          PRNUM: ${{ github.event.pull_request.number }}