Bump to 6.0.0 (#443)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0072bcb..9742ee2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,4 @@
-## 6.0.0-dev
+## 6.0.0
 
 * Require Dart 2.17
 * Add support to GFM extension for GitHub task lists (aka checkboxes).  These
diff --git a/lib/src/version.dart b/lib/src/version.dart
index 92964be..0773426 100644
--- a/lib/src/version.dart
+++ b/lib/src/version.dart
@@ -1,2 +1,2 @@
 // Generated code. Do not modify.
-const packageVersion = '6.0.0-dev';
+const packageVersion = '6.0.0';
diff --git a/pubspec.yaml b/pubspec.yaml
index 0dc576f..4a69ba5 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: markdown
-version: 6.0.0-dev
+version: 6.0.0
 
 description: A portable Markdown library written in Dart that can parse
  Markdown into HTML.