updated readme

README.md

@@ -1,17 +1,43 @@
 # flutter-action
 
-This action sets up a flutter environment for use in actions.
+This action sets up a flutter environment for use in actions. It works on Linux, Windows, and macOS.
 
 # Usage
 
 ```yaml
 steps:
-- uses: actions/checkout@latest
+- uses: actions/checkout@master
 - uses: actions/setup-java@v1
   with:
-    version: '8.x'
+    java-version: '12.x'
 - uses: subosito/flutter-action@master
   with:
     version: '1.7.8+hotfix.4'
+- run: flutter pub get
+- run: flutter test
 - run: flutter build apk
 ```
+
+Matrix Testing:
+
+```yaml
+jobs:
+  test:
+    name: Test on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+      - uses: actions/checkout@master
+      - uses: actions/setup-java@v1.0.1
+        with:
+          java-version: '12.x'
+      - uses: subosito/flutter-action@master
+        with:
+          version: '1.7.8+hotfix.4'
+      - run: flutter pub get
+      - run: flutter test
+      - run: flutter build apk
+```
+