add github action

.github/workflows/scala.yml

@@ -0,0 +1,31 @@
+name: Scala CI
+
+on:
+  push:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: Set up JDK 11
+      uses: actions/setup-java@v2
+      with:
+        java-version: '11'
+        distribution: 'adopt'
+        
+    - name: Cache sbt
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.sbt
+          ~/.cache/coursier/v1
+        key: scala
+        
+    - name: Run tests
+      run: sbt "+scalafixAll --check" +scalafmtCheck "+test"