Is your feature request related to a problem? Please describe.
I'm using vite to build a library, and sometimes the library requires a dozen lines of simple styles. After building, a style.css file will be generated. But I think it is not necessary to generate two files, it may be enough to generate only one file. Is there any way to add style.css to the target js file?

The styleInject helper function is used in rollup and babel plug-ins. In iife/umd mode, the style is automatically injected when library loaded.