actions: combine docker workflows

.github/workflows/docker.yml

@@ -0,0 +1,31 @@
+on:
+  push:
+    branches:
+    - 'main'
+    tags:
+    - '*'
+name: docker-publish-tags
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - uses: docker/login-action@v1
+      with:
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+
+    - uses: docker/metadata-action@v3
+      id: meta
+      with:
+        images: willnorris/imageproxy
+
+    - uses: docker/build-push-action@v1
+      with:
+        context: .
+        push: true
+        tags: ${{ steps.meta.output.tags }}
+        labels: ${{ steps.meta.output.labels }}