ci: add workflow to label PRs needing rebase (#460)

Author: MickaelCa

.github/workflows/rebase-needed.yml

@@ -0,0 +1,29 @@
+name: PR Needs Rebase
+
+on:
+  workflow_dispatch: {}
+  schedule:
+    - cron: '0 * * * *'
+
+permissions:
+  pull-requests: write
+
+jobs:
+  label-rebase-needed:
+    runs-on: ubuntu-latest
+    if: github.repository == 'coderamp-labs/gitingest'
+
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
+      cancel-in-progress: true
+
+    steps:
+      - name: Check for merge conflicts
+        uses: eps1lon/actions-label-merge-conflict@v3
+        with:
+          dirtyLabel: 'rebase needed :construction:'
+          repoToken: '${{ secrets.GITHUB_TOKEN }}'
+          commentOnClean: This pull request has resolved merge conflicts and is ready for review.
+          commentOnDirty: This pull request has merge conflicts that must be resolved before it can be merged.
+          retryMax: 30
+          continueOnMissingPermissions: false