Docs improvement: Next.js's cache needs to be cleared after registering the plugin

[guansss]

Hi, I was trying to use @swc-jotai/debug-label in my Next.js project, and after installing it, all my atoms were still displayed as "unlabeled" in the DevTools.

After some searching and debugging, I found that I should delete the .next folder because Next.js seems to cache the compilation result, and adding a SWC plugin will not invalidate the cache.

I think this can be added to the docs to help others.

[Thisen]

Feel free to PR!