Add greetings action

Remove configuration files of unused probot apps too.

Signed-off-by: JoeLametta <JoeLametta@users.noreply.github.com>

.github/workflows/greetings.yml

@@ -0,0 +1,16 @@
+name: Greetings
+
+on: [pull_request, issues]
+
+jobs:
+  greeting:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/first-interaction@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        issue-message: |
+          👋 Thanks for opening your first issue here! If you're reporting a 🐞 bug, please make sure you include steps to reproduce it. We get a lot of issues on this repo, so please be patient and we will get back to you as soon as we can.
+
+          To help make it easier for us to investigate your issue, please follow the [contributing instructions](https://github.com/whipper-team/whipper#bug-reports--feature-requests).
+        pr-message: '💖 Thanks for opening your first pull request here! 💖'