fix #56 new theme for RSSAid (#57)

* feat: new theme

* feat: code refactor

* feat: remove hardcode theme

* feat: use not found widget

* feat: remove all snack bar and use oktoast instead

lib/l10n/app_en.arb

@@ -3,7 +3,7 @@
   "notfoundinClipboard": "No links detected on clipboard",
   "fromClipboard": "Import from clipboard",
   "inputbyKeyboard": "Import from plain text",
-  "notfound": "Not found",
+  "notfound": "Not Found",
   "addConfig": "Create configuration",
   "submitNewRules": "Submit new rules",
   "whichSupport": "View supported rules",

lib/main.dart

@@ -8,6 +8,7 @@ import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:oktoast/oktoast.dart';
 import 'package:rssaid/shared_prefs.dart';
 import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:rssaid/theme.dart';
 import 'package:rssaid/views/home.dart';
 
 Future<void> main() async {
@@ -38,10 +39,8 @@ class RSSAidApp extends StatelessWidget {
         Locale('en', ''), // English, no country code
         Locale('zh', ''), // Chinese, no country code
       ],
-      theme: ThemeData(
-          useMaterial3: true,
-          brightness: Brightness.light, //指定亮度主题，有白色/黑色两种可选。
-      ), //这里我们选浅蓝色为强调色值。
+      theme: MaterialTheme(Theme.of(context).textTheme).light(),
+      darkTheme: MaterialTheme(Theme.of(context).textTheme).dark(),
       home: HomePage(),
     ));
   }