supported sdk version range extended to 4.0

Author: csongorkeller

pubspec.yaml

@@ -4,7 +4,7 @@ version: 2.3.0
 homepage: 'https://github.com/csongorkeller/flutter_open_weather_package'
 
 environment:
-  sdk: ">=2.19.0 <3.0.0"
+  sdk: ">=2.19.0 <4.0.0"
   flutter: ">=1.17.0"
 
 dependencies: