Move away from Travis to Github actions

.github/workflows/welcome.yml

@@ -0,0 +1,13 @@
+name: Welcome
+
+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 submitting your first issue, we will have a look as quickly as possible.'
+          pr-message: 'Thanks so much for your contribution, really appreciated! We will have a look and merge it if everything checks out!'