Add docker image builder action

.github/workflows/docker-image-build.yml

@@ -0,0 +1,37 @@
+
+name: Docker Image Builder for SenseLink
+
+on:
+  # Allow manual dispatch
+  workflow_dispatch:
+  # Run only manually for now
+#  release:
+#    types: [published, released]
+
+jobs:
+
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up QEMU
+      uses: docker/setup-qemu-action@v1
+    - name: Set up Docker Buildx
+      id: buildx
+      uses: docker/setup-buildx-action@v1
+    - name: Create builder
+      run: docker buildx create --name senselink-builder
+    - name: Use senselink-builder
+      run: docker buildx use senselink-builder
+    - run: docker buildx inspect --bootstrap
+    - name: Define latest version via tag
+      run: echo "latest=$(git describe --tags $(git rev-list --tags --max-count=1))" >> $GITHUB_ENV
+    - name: Log in to Docker Hub
+      uses: docker/login-action@v1.14.1
+      with:
+        username: theta142
+        password: ${{ secrets.DOCKER_HUB_TOKEN }}
+    - name: Build SenseLink for various platforms
+      run: docker buildx build --platform linux/amd64,linux/arm64,linux/arm/v7 -t theta142/senselink:${{ env.latest }} -t theta142/senselink:latest --push .