Fix links to codegen readme (#661)

Author: atlv24

.github/pull_request_template.md

@@ -13,7 +13,7 @@
 - Are you modify generated code?
 - Have you modified the templates and run the code generator?
 
-See https://github.com/bitshifter/glam-rs/blob/main/codegen/README.md for details.
+See https://github.com/bitshifter/glam-codegen/blob/main/README.md for details.
 
 ## Testing and linting
 

CONTRIBUTING.md

@@ -55,4 +55,4 @@ Also run `cargo fmt` and `cargo clippy` on any new code.
 [open an issue]: https://GitHub.com/bitshifter/glam-rs/issues/new
 [ask a question]: https://github.com/bitshifter/glam-rs/discussions/new?category=q-a
 [suggest a new feature]: https://github.com/bitshifter/glam-rs/discussions/new?category=ideas
-[codegen README]: codegen/README.md
+[codegen README]: https://github.com/bitshifter/glam-codegen/blob/main/README.md