Revert "Disabled greeting action (#38)" (#50)

This reverts commit 82f0618.

.github/workflows/greetings.yml

@@ -0,0 +1,21 @@
+---
+name: Greetings
+
+on: [pull_request, issues]
+
+jobs:
+  greeting:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/first-interaction@v1
+      if: env.month != 'Oct'
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        issue-message: 'Thank you for your first issue! 😊🕹️'
+        pr-message: 'Thank you for contributing to this project! 😊🕹️'
+    - uses: actions/first-interaction@v1
+      if: env.month == 'Oct'
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        issue-message: 'Thank you for your first issue! Happy Hacktoberfest!!! 🎃👕🕹️'
+        pr-message: 'Thank you for contributing to this project. Happy Hacktoberfest!!! 🎃👕🕹️'