add Github Actions

Signed-off-by: Christian Rebischke <chris@nullday.de>

.github/workflows/main.yml

+name: Github-Actions
+
+on: [push, pull_request]
+
+jobs:
+  ci-test:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: make ci-test
+      run: make ci-test