fix build error (install qemu-user-static)

.github/workflows/build.yml

@@ -1,11 +1,13 @@
 name: build
 on:
+  workflow_dispatch:
   schedule: [{ cron: "0 21 * * sun" }] # Every Monday at 6am Asia/Tokyo UTC+9
 jobs:
   main:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - run: sudo apt-get install -y qemu-user-static
       - run: docker login docker.pkg.github.com -u "${GITHUB_ACTOR}" -p "${{ github.token }}"
       - run: bin/build
       - run: docker-compose push

README.md

@@ -33,6 +33,7 @@ rsync -a dist/ /path/to/sd/
 - ruby
 - ssh-keygen
 - bash
+- qemu-user-static
 
 ### WiFi の設定