Add required fields to pubspec.yaml.s
diff --git a/pubspec.yaml b/pubspec.yaml
index 4084b0b..558fc7b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,10 @@
 name: characters
 version: 0.3.0
+description: String replacement with operations that are Unicode/grapheme cluster aware.
+author: Dart Team <misc@dartlang.org>
+homepage: https://www.github.com/dart-lang/characters
+
 environment:
-  sdk: "^2.5.0"
+  sdk: ">=2.5.0 <3.0.0"
 dev_dependencies:
   test: "^1.6.0"