ci: add automated thank you workflow for merged PRs

Signed-off-by: Shivansh Sahu <sahushivansh142@gmail.com>

Author: shivansh-gohem

.github/workflows/thank-you.yaml

@@ -0,0 +1,50 @@
+name: Contributor Thank You
+
+on:
+  pull_request_target:
+    types:
+      - closed
+
+permissions:
+  pull-requests: write
+
+jobs:
+  thank-you:
+    # Only run if the PR was actually merged (not just closed without merging)
+    if: github.event.pull_request.merged == true
+    runs-on: ubuntu-latest
+    steps:
+      - name: Leave a Thank You Comment
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const creator = context.payload.pull_request.user.login;
+            
+            // Skip bots to avoid comment loops
+            if (creator.endsWith('[bot]')) {
+              console.log('Skipping bot account.');
+              return;
+            }
+
+            // Search for previous merged PRs by this user in this repo
+            const query = `repo:${context.repo.owner}/${context.repo.repo} type:pr is:merged author:${creator}`;
+            const result = await github.rest.search.issuesAndPullRequests({ q: query });
+            const mergedCount = result.data.total_count;
+
+            let message = '';
+
+            // If count is 1, this current PR is their very first merged PR!
+            if (mergedCount === 1) {
+              message = `### 🎉 Congratulations on your first merged Pull Request, @${creator}! \n\nWelcome to the **PipeCD** community! We are absolutely thrilled to have you here. Thank you for taking the time to contribute to the project.\n\nWe hope this is the first of many! 🚀\n\n*(If you haven't already, feel free to join our [Community Slack/Discord](#) to say hi!)*`;
+            } else {
+              // Returning contributor
+              message = `### Awesome work, @${creator}! 🎉\n\nThank you for another great contribution to PipeCD! Your continued support and dedication help make this project better for everyone. 🙌`;
+            }
+
+            // Post the comment to the PR
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.pull_request.number,
+              body: message
+            });