Update welcome.yml

Author: elliotrichards

.github/workflows/welcome.yml

@@ -8,3 +8,8 @@ jobs:
   welcome:
     name: Post welcome comment
     runs-on: ubuntu-latest
+    steps:
+      - run: gh pr comment "$PR_URL" --body "Welcome to the repository!"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_URL: ${{ github.event.pull_request.html_url }}