Added GitHub action for container build

.github/workflows/container-build.yml

@@ -0,0 +1,21 @@
+name: container-build
+on:
+  push:
+    paths:
+      - 'data/Dockerfiles/parsedmarc/**'
+  schedule:
+    - cron: '0 0 14 * *'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+          repository: patschi/parsedmarc-dockerized
+          tags: latest