Provide warning for consumers that are using our old CSS tokens

[thatblindgeye]

This pertains tot he topic of our new token documentation. We should at the very least have a codemod that will throw a warning if a consumer is using our old CSS tokens and to link them to any applicable token documentation.

It was noted during planning topics discussion that it can be dangerous for us to provide suggestions of what exact token a consumer should use instead, so it could be safer to at least get consumers to think about why they're using a specific CSS token and let them read through our token docs.