Enable build runner workflow

.github/workflows/build-runner.yml

@@ -0,0 +1,22 @@
+on:
+  push:
+    branches:
+    - master
+    paths:
+    - 'runner/**'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    name: Build runner
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Build container image
+      run: make docker-build
+      working-directory: runner
+    - name: Docker Login
+      run: docker login -u summerwind -p ${{ secrets.DOCKER_ACCESS_TOKEN }}
+    - name: Push container image
+      run: make docker-push
+      working-directory: runner