add support for github actions

.github/workflows/build.yaml

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
new file mode 100644
index 0000000..4d33943
--- /dev/null
+++ b/.github/workflows/build.yaml
@@ -0,0 +1,29 @@
+name: Dart
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    container:
+      image:  google/dart:beta
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: pub get
+        run: pub get
+
+      - name: dart format
+        run: dart format --output=none --set-exit-if-changed .
+
+      - name: dart analyze
+        run: dart analyze
+
+      - name: dart test
+        run: dart test