Crossbuild docker image for different architectures (#55)

* Crossbuild docker image

* Fix yaml syntax

* Github Actions timeout disabled

* Add linux/386, linux/arm/v6, linux/arm/v7, linux/ppc64le, linux/s390x docker images

* Remove linux/386, linux/ppc64le, linux/s390x docker images

* Remove "Github Packages" from build step name

Co-authored-by: Chris C. <twin@twinnation.org>

* Split workflow file to test/docker

* Forward RELEASE variable to GITHUB_ENV

* Bring back timeout for tests

Co-authored-by: Chris C. <twin@twinnation.org>

.github/workflows/docker.yml

@@ -0,0 +1,33 @@
+name: docker
+on:
+  release:
+    types: [published]
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v2
+      - name: Get image repository
+        run: echo IMAGE_REPOSITORY=$(echo ${{ github.repository }} | tr '[:upper:]' '[:lower:]') >> $GITHUB_ENV
+      - name: Get the release
+        run: echo RELEASE=${GITHUB_REF/refs\/tags\//} >> $GITHUB_ENV
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: Login to Docker Registry
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME  }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+      - name: Build and push docker image
+        uses: docker/build-push-action@v2
+        with:
+          platforms: linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64
+          pull: true
+          push: true
+          tags: |
+            ${{ env.IMAGE_REPOSITORY }}
+            ${{ env.IMAGE_REPOSITORY }}:${{ env.RELEASE }}