add usage trend

[cwtuan]

I'm an active user of clsx and a big fan of its speed and size advantages over classnames. I've noticed that clsx's usage trend is gaining more popularity, which is fantastic!

clsx has proven to be a faster and smaller drop-in replacement for the classnames module. However, many new users may not be aware of this fact and might benefit from a simple comparison to make an informed choice. By including this link in the documentation, we can help new users understand the advantages of using clsx.

I appreciate the effort you put into maintaining the clsx package and helping the developer community. Thank you for your time and consideration.