build: notify via slack when review-wanted

I have noticed we don't have a usual workflow for
review-wanted PRs. So, in other words the label
is not useful as it should be. This commit notify
via Slack (#node-core) whenever this label is placed
either on an issue or in a PR.

PR-URL: nodejs#55102
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

.github/workflows/notify-on-review-wanted.yml

@@ -0,0 +1,40 @@
+name: Notify on Review Wanted
+on:
+  issues:
+    types: [labeled]
+  pull_request_target:
+    types: [labeled]
+
+permissions:
+  contents: read
+
+jobs:
+  notifyOnReviewWanted:
+    name: Notify on Review Wanted
+    if: github.repository == 'nodejs/node' && github.event.label == 'review wanted'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Determine PR or Issue
+        id: define-message
+        run: |
+          if [[ -n "${{ github.event.pull_request.number }}" ]]; then
+            number="${{ github.event.pull_request.number }}"
+            link="https://github.com/${{ github.repository }}/pull/$number"
+            echo "message=The PR (#$number) requires review from Node.js maintainers. See: $link" >> "$GITHUB_OUTPUT"
+            echo "title=${{ github.actor }} asks for attention on pull request #$number" >> "$GITHUB_OUTPUT"
+          else
+            number="${{ github.event.issue.number }}"
+            link="https://github.com/${{ github.repository }}/issues/$number"
+            echo "message=The issue (#$number) requires review from Node.js maintainers. See: $link" >> "$GITHUB_OUTPUT"
+            echo "title=${{ github.actor }} asks for attention on issue #$number" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Slack Notification
+        uses: rtCamp/action-slack-notify@4e5fb42d249be6a45a298f3c9543b111b02f7907  # 2.3.0
+        env:
+          SLACK_COLOR: '#DE512A'
+          SLACK_ICON: https://github.com/nodejs.png?size=48
+          SLACK_TITLE: ${{ steps.define-message.outputs.title }}
+          SLACK_MESSAGE: ${{ steps.define-message.outputs.message }}
+          SLACK_USERNAME: nodejs-bot
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK }}