fix links

Author: BirjuVachhani

docs/get_started.mdx

@@ -61,3 +61,5 @@ You can use `BoxTransformer.move` to move a box.
 
   result.position; // the new position of the box
 ```
+
+[boxTransform]: https://github.com/hyper-designed/box_transform

docs/index.mdx

@@ -57,8 +57,8 @@ See [DEVELOPMENT.md][development] for development setup.
 
 Feel free to join our Discord server for any inquiries or support: https://discord.gg/yrahEhCqTJ
 
-[github]  https://github.com/hyper-designed/box_transform
-[pubdev]  https://pub.dev/packages/box_transform
-[demo]  https://boxtransform-demo.hyperdesigned.dev
-[contributing]  https://github.com/hyper-designed/box_transform/blob/main/CONTRIBUTING.md
-[development]  https://github.com/hyper-designed/box_transform/blob/main/development.md
+[github]: https://github.com/hyper-designed/box_transform
+[pubdev]:  https://pub.dev/packages/box_transform
+[demo]:  https://boxtransform-demo.hyperdesigned.dev
+[contributing]:  https://github.com/hyper-designed/box_transform/blob/main/CONTRIBUTING.md
+[development]:  https://github.com/hyper-designed/box_transform/blob/main/development.md