Adds manually-triggered GH workflow for release builds

.github/workflows/docker-release.yml

@@ -0,0 +1,32 @@
+name: docker
+
+on:
+  workflow_dispatch:
+    inputs:
+      tags:
+        description: 'Docker tags'
+        required: true
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout code
+        uses: actions/checkout@v2
+      - name: setup platform emulator
+        uses: docker/setup-qemu-action@v1
+      - name: setup multi-arch docker build
+        uses: docker/setup-buildx-action@v1
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: build & push images
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          file: ./Dockerfile
+          platforms: linux/amd64,linux/arm,linux/arm64/v8
+          push: true
+          tags: ${{ github.event.inputs.tags }}