ignore .dart_tool dir

pkgs/io/.gitignore

diff --git a/pkgs/io/.gitignore b/pkgs/io/.gitignore
index dd3394e..01d42c0 100644
--- a/pkgs/io/.gitignore
+++ b/pkgs/io/.gitignore
@@ -1,3 +1,4 @@
+.dart_tool/
 .pub/
 .packages
 pubspec.lock