Added greetings workflow

.github/workflows/greetings.yml

@@ -0,0 +1,20 @@
+name: Greetings
+
+on:
+  pull_request:
+    branches: [ main ]
+  issues:
+    branches: [ main ]
+
+jobs:
+  greeting:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+    - uses: actions/first-interaction@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        issue-message: 'Thank you for the issue! This issue will be addressed in a reasonable amount of time.'
+        pr-message: 'Thank you for the pull request! This contribution will be addressed in a reasonable amount of time.'