add diff generating workflow to help PR reviews

.github/workflows/diff.yml

@@ -0,0 +1,34 @@
+# Print the diff between the official and the generated file
+name: Diff
+on:
+  pull_request:
+    branches: [ main ]
+
+permissions:
+  contents: read
+
+jobs:
+  diff:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
+
+      - name: Generate Diff
+        id: diff
+        run: |
+          bash dockerhub_doc_config_update.sh
+          diff=$(git --no-pager diff -U0 --ignore-matching-lines='^GitCommit:' --no-index official-eclipse-temurin eclipse-temurin)
+          echo "diff=$diff" >> "$GITHUB_OUTPUT"
+    
+      - name: Print diff as a comment
+        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
+        if: ${{ steps.diff.outputs.diff != '' }}
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            github.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: '```diff\n' + ${{ steps.diff.outputs.diff }} + '\n```'
+            });