Integrate with Vite

It will be nice if we can integrate EncreCSS to Vite (in form of Vite plugin), so that we don't have to run a separate command for EncreCSS.

My idea is that, EncreCSS can get the scanning source from Vite like UnoCSS does: https://unocss.dev/guide/extracting#extracting-from-build-tools-pipeline