rewrite flutter-action

.github/workflows/workflow.yml

@@ -7,16 +7,10 @@ jobs:
     strategy:
       matrix:
         operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        channel: [stable, beta, dev]
     steps:
     - name: Checkout
       uses: actions/checkout@v2
-    - name: Set Node.js 10.x
-      uses: actions/setup-node@v1
+    - uses: ./
       with:
-        node-version: 10.x
-    - name: npm install
-      run: npm install
-    - name: Lint
-      run: npm run format-check
-    - name: npm test
-      run: npm test
+        channel: ${{ matrix.channel }}