Add PR comment workflow

Author: swissspidy

.github/workflows/reusable-welcome-new-contributors.yml

@@ -0,0 +1,19 @@
+name: Welcome New Contributors
+
+on:
+  workflow_call:
+
+jobs:
+  welcome:
+    runs-on: ubuntu-latest
+    steps:
+      - name: First Interaction
+        uses: actions/first-interaction@v3
+        with:
+          repo_token: ${{ secrets.GITHUB_TOKEN }}
+          pr_message: |
+            Hello! 👋
+
+            Thanks for opening this pull request! Please check out our [contributing guidelines](https://make.wordpress.org/cli/handbook/contributions/contributing/). We appreciate you taking the initiative to contribute to this project.
+
+            Contributing isn't limited to just code. We encourage you to contribute in the way that best fits your abilities, by writing tutorials, giving a demo at your local meetup, helping other users with their support questions, or revising our documentation.

.github/workflows/sync-workflows.yml

@@ -24,6 +24,7 @@ jobs:
             ^.editorconfig
             ^.github/workflows/code-quality.yml
             ^.github/workflows/regenerate-readme.yml
+            ^.github/workflows/welcome-new-contributors.yml
             ^AGENTS.md
           TARGET_REPOS: |
             wp-cli/admin-command

.github/workflows/welcome-new-contributors.yml

@@ -0,0 +1,12 @@
+name: Welcome New Contributors
+
+on:
+  pull_request_target:
+    types: [opened]
+    branches:
+      - main
+      - master
+
+jobs:
+  welcome:
+    uses: wp-cli/.github/.github/workflows/reusable-welcome-new-contributors.yml@main