Setting Custom Babel

[aesop-igaw]

Describe the problem

I want to set babel plugins but I don't know how to do...;;
If I use browser with using ES5 like supporting only CJS not ESM, How can I use sveltekit application?

Describe the proposed solution

Make a option for babel setting in svelte.config.js plz

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

[Conduitry]

Duplicate of #12.