Add github actions (#28)

.github/workflows/flutter.yml

@@ -0,0 +1,27 @@
+name: Flutter CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    steps:
+    - uses: actions/checkout@v2
+    - uses: subosito/flutter-action@v1
+      with:
+        channel: 'beta'
+
+    # Get flutter dependencies.
+    - run: flutter packages get
+
+    # Check for any formatting issues in the code.
+    - run: flutter format --set-exit-if-changed .
+
+    # Statically analyze the Dart code for any errors.
+    - run: flutter analyze .