Add CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,24 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - '**'
+      - '!master'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+        with:
+          platforms: amd64,arm64,arm/v7,s390x,ppc64le
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Build images
+        run: docker buildx bake --pull

.github/workflows/publish.yml

@@ -2,7 +2,8 @@ name: Publish
 
 on:
   push:
-    branches: master
+    branches:
+      - 'master'
 
 jobs:
   build: