Adds automated Docker image release GitHub action

.github/workflows/release.yml

@@ -0,0 +1,25 @@
+name: release
+on:
+  release:
+    types: [published]
+jobs:
+  push_server_to_docker_registry:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: docker/build-push-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+          repository: oxigraph/oxigraph
+          tag_with_ref: true
+  push_wikibase_to_docker_registry:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: docker/build-push-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+          repository: oxigraph/oxigraph-wikibase
+          tag_with_ref: true