Include `svelte.config.js` in `tsconfig.json`

[dummdidumm]

Describe the problem

We had to revert #11886 in #11908 because it's a breaking change but it's probably good to include it

Describe the proposed solution

Include it

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

[benmccann]

We should also consider setting recommended-type-checked in create-svelte when the user sets up eslint.