docker: build with github actions

.github/workflows/docker.yml

@@ -0,0 +1,32 @@
+name: Docker
+
+on:
+  push:
+    paths-ignore:
+      - '**.md'
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+    env:
+      TZ: Asia/Taipei
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Setup QEMU
+        uses: docker/setup-qemu-action@v2
+        with:
+          platforms: linux/amd64
+
+      - name: Setup Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Build Docker Image
+        uses: docker/build-push-action@v3
+        with:
+          context: .
+          file: docker/Dockerfile
+          tags: phantun
+          platforms: linux/amd64

docker/README.md

@@ -1,3 +1,11 @@
 # phantun (docker)
 
+## Build
+
+```sh
+docker build -t phantun -f docker/Dockerfile .
+```
+
+## Usage
+
 It is recommended to use docker-compose, see [docker-compose.yml](docker-compose.yml) for details.