chore: 添加代码风格检查

Author: Mark Lin

Diff for: analysis_options.yaml

@@ -0,0 +1,7 @@
+include: package:lint/analysis_options.yaml
+
+analyzer:
+  strong-mode:
+    implicit-casts: true
+  enable-experiment:
+    - extension-methods

Diff for: pubspec.lock

@@ -60,6 +60,13 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  lint:
+    dependency: "direct dev"
+    description:
+      name: lint
+      url: "https://pub.flutter-io.cn"
+    source: hosted
+    version: "1.5.3"
   matcher:
     dependency: transitive
     description:
@@ -143,5 +150,5 @@ packages:
     source: hosted
     version: "2.1.0"
 sdks:
-  dart: ">=2.12.0-0.0 <3.0.0"
-  flutter: ">=1.17.0"
+  dart: ">=2.12.0 <3.0.0"
+  flutter: ">=2.0.1"

Diff for: pubspec.yaml

@@ -6,7 +6,7 @@ homepage:
 
 environment:
   sdk: ">=2.7.0 <3.0.0"
-  flutter: ">=1.17.0"
+  flutter: ">=2.0.1"
 
 dependencies:
   flutter:
@@ -15,6 +15,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  lint: ^1.5.3
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec