Add docker action

Signed-off-by: trivernis <trivernis@protonmail.com>

.github/workflows/docker.yml

@@ -0,0 +1,45 @@
+name: Build Docker Image
+
+on:
+  push:
+    branches: [ main, actions ]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+
+      - name: Copy Repo Files
+        uses: actions/checkout@master
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.CR_PAT }}
+
+      - name: Login to Portus
+        uses: docker/login-action@v1
+        with:
+          registry: https://flotte-docker-registry.spdns.org/
+          username: ${{ secrets.PORTUS_USERNAME }}
+          password: ${{ secrets.PORTUS_PASSWORD }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          file: ./Dockerfile
+          platforms: linux/amd64,linux/arm/v7,linux/arm64
+          push: true
+          tags: |
+            flotte-docker-registry.spdns.org/frontend-server:latest
+            ghcr.io/flotte-meets-hwr-db/frontend/frontend-server