Use GH actions to build container image (#341)

* build frontend container image via GH actions

.github/workflows/osrm-frontend-docker.yml

@@ -0,0 +1,41 @@
+name: build and publish container image
+on:
+  push:
+    branches:
+      - gh-pages
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:       
+      - name: Check out the repo
+        uses: actions/checkout@v2
+
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ghcr.io/${{ github.repository }}          
+          flavor: |
+            latest=true
+
+
+      - name: Log in to GitHub Docker Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+
+      - name: Build container image 
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          file: ./docker/Dockerfile
+          tags: ${{ steps.meta.outputs.tags  }}
+
+
+
+