add a github action to build the docker image

.github/workflows/build.yaml

@@ -0,0 +1,10 @@
+name: build
+on: [push, pull_request]
+jobs:
+  build:
+    name: build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Build the Docker image
+        run: docker build .