Support latest args version

pkgs/markdown/pubspec.yaml

diff --git a/pkgs/markdown/pubspec.yaml b/pkgs/markdown/pubspec.yaml
index 17ec8e4..fa02b1d 100644
--- a/pkgs/markdown/pubspec.yaml
+++ b/pkgs/markdown/pubspec.yaml
@@ -6,7 +6,7 @@
 environment:
   sdk: '>=1.12.0 <2.0.0'
 dev_dependencies:
-  args: '^0.13.3+1'
+  args: '>=0.13.3+1 <2.0.0'
   # Only for example/app.dart.
   browser: any
   collection: '^1.2.0'