Add CI job to test the lib on varouis os and sdk versions

.github/workflows/build.yml

@@ -3,7 +3,26 @@ name: Dart CI
 on: [ push, pull_request ]
 
 jobs:
-  test:
+  test-os:
+    timeout-minutes: 5
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+        sdk: [ stable, beta, dev ]
+
+    container:
+      image: dart:${{ matrix.sdk }}
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install dependencies
+        run: dart pub get
+      - name: Run tests
+        run: dart pub run test
+
+  test-versions:
     timeout-minutes: 5
     runs-on: ubuntu-latest