Add Github Actions workflow to automatically build a Docker image on pushes to master

.github/workflows/build.yml

@@ -0,0 +1,33 @@
+name: Build Docker Image
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    name: Build Docker image
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to Gitlab
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ secrets.DOCKERHUB_PROJECT }}:latest