Fix typo: "packjage_config" (dart-lang/package_config#113)

diff --git a/pkgs/package_config/lib/src/package_config.dart b/pkgs/package_config/lib/src/package_config.dart
index 8210132..3c5cc51 100644
--- a/pkgs/package_config/lib/src/package_config.dart
+++ b/pkgs/package_config/lib/src/package_config.dart
@@ -204,7 +204,7 @@
   /// Extra data associated with the package configuration.
   ///
   /// The data may be in any format, depending on who introduced it.
-  /// The standard `packjage_config.json` file storage will only store
+  /// The standard `package_config.json` file storage will only store
   /// JSON-like list/map data structures.
   Object? get extraData;
 }