chore: set max SDK version to <3.0.0, and adjust other dependencies (#229)

diff --git a/pubspec.yaml b/pubspec.yaml
index 420af6b..f9611eb 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml

@@ -1,26 +1,27 @@
 name: markdown
-version: 2.0.1
-author: Dart Team <misc@dartlang.org>
+version: 2.0.2
+
 description: A library for converting markdown to HTML.
+author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/markdown
 
 executables:
   markdown:
 
 environment:
-  sdk: '>=2.0.0-dev <2.0.0'
+  sdk: '>=2.0.0-dev <3.0.0'
 
 dependencies:
-  args: '^1.0.0'
-  charcode: '^1.1.0'
+  args: ^1.0.0
+  charcode: ^1.1.0
 
 dev_dependencies:
-  build_runner: ^0.8.2
+  build_runner: ^0.9.1
   build_web_compilers: ^0.4.0
-  collection: '^1.2.0'
-  expected_output: '^1.1.0'
+  collection: ^1.2.0
+  expected_output: ^1.2.1
   html: '>=0.12.2 <0.14.0'
-  js: '^0.6.1'
-  path: '^1.3.1'
-  test: '>=0.12.42 <2.0.0'
-  yaml: '^2.1.8'
+  js: ^0.6.1
+  path: ^1.3.1
+  test: ^1.2.0
+  yaml: ^2.1.8