Upgrade to null safety

packages/css_colors/CHANGELOG.md

@@ -0,0 +1,12 @@
+## 1.1.0
+
+- Add support for null safety
+- Update SDK constraints
+
+## 1.0.0
+
+- Add SDK constraints for Dart and Flutter
+
+## 1.0.0
+
+- Initial version

packages/css_colors/pubspec.yaml

@@ -2,12 +2,12 @@ name: css_colors
 author: Flutter Authors <flutter-dev@googlegroups.com>
 description: Defines constants for the CSS Colors
 homepage: https://github.com/flutter/css_colors
-version: 1.0.2
+version: 1.1.0
+
+environment:
+  sdk: '>=2.12.0-29.10.beta <3.0.0'
+  flutter: ">=1.0.0"
 
 dependencies:
   flutter:
     sdk: flutter
-
-environment:
-  sdk: ">=1.19.0 <3.0.0"
-  flutter: ">=0.4.4 <2.0.0"