feat: update starlight (#1219)

- Updated starlight version introduces `<Code />` component which lets
us use the same syntax theme as the rest of the docs. Currently the
theme is different when using our custom [`<EmbeddedSnippet
/>`](https://union.build/docs/integration/solidity/) vs. directly adding
code to markdown. With this update they're the same.
- Remove anchor tag reset in docs. Links are hard to distinguish from
real text in the docs when dark mode is on so underline fixes this
issue:
![CleanShot 2024-01-27 at 18 34
58](https://github.com/unionlabs/union/assets/23618431/fffa118e-6080-4818-9408-4664987e271f)
- Add `reset.d.ts` to `tsconfig.json` `files`. Previously it was not
being used since it wasn't listed there.

This pr improves performance score from 71 to 93 on Google's Pagespeed
Insights:

- before:
https://pagespeed.web.dev/analysis/https-union-build/236e9s4vso?form_factor=mobile
- after:
https://pagespeed.web.dev/analysis/https-ef14a83f-docs-19u-pages-dev/v4aeb4ghko?form_factor=mobile