Introduce github actions (#375)

.github/workflows/docker.yml

@@ -0,0 +1,20 @@
+name: Docker
+
+on:
+  push:
+    branches: [ master ]
+#  pull_request:
+#    branches: [ master ]
+
+jobs:
+
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Install
+      run: curl -sfL https://raw.githubusercontent.com/ldez/seihon/master/godownloader.sh | bash -s -- -b $GOPATH/bin v0.5.1
+    - name: Build
+      run: make publish-images