adds github CI workflow

.github/workflows/main.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+jobs:
+  test:
+    name: unit-test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v1
+        with:
+          java-version: "12.x"
+      - uses: subosito/flutter-action@v1.5.3
+        with:
+          flutter-version: 2.0.4
+      - name: Install dependencies
+        run: flutter pub get
+      - name: Analyze Dart code
+        run: flutter analyze -v
+      - name: Run tests
+        run: flutter test --coverage
+      - name: Coveralls
+        uses: coverallsapp/github-action@1.1.3
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}