Added Github Workflow for Greeting contributor on their first PR merge

.github/workflows/greet_on_first_merge.yml

@@ -0,0 +1,38 @@
+name: Greet on User First PR Merge
+
+on:
+  pull_request:
+    types: [closed]
+
+jobs:
+  greet:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/github-script@v4
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const prNumber = context.payload.pull_request.number;
+            const authorLogin = context.payload.pull_request.user.login;
+
+            const firstPR = await github.issues.listForRepo({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_requests: {
+                state: 'closed',
+                author: authorLogin,
+              },
+            });
+
+            console.log(firstPR.data.length); 
+
+            if (firstPR.data.length === 1) {
+              const greetingMessage = ` Congratulations, @${authorLogin} for your first pull request merge in this repository! 🎉🎉. Thanks for your contribution to JSON Schema! `;
+
+              await github.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: prNumber,
+                body: greetingMessage
+              });
+            }