feat: added rollupOptions to config for overriding them

[alyssa-murati]

Hey all,

Simple PR here to add rollupOptions to just override input and output - there's a lot of case by case need for these options such as splitting module entries for other purposes.

Please any suggestions to make it better.

Thanks

[axe-me]

Thanks for your contribution, Can you also add some docs to the readme file?

[axe-me]

I believe you can simply append your rollupOptions to the root vite config. Vite will respect your config and merge all the configs.