Support embedded replicas

[vicary]

Summary

1. The default import of @libsql/client here resolves to web.js, which contains no support of the file: protocol.
2. The requirement of manual closing when using the client option is unrealistic for most use cases, without Kysely exposing some kind of "on destroy" callback.

Suggested Solution

1. Add a new option createClient as a callback

[vicary]

Turns out it's unnecessary because

1. web.js is imported because of Deno, Node is fine.
2. Although client still makes no sense for manual closing, it should be a PR for @libsql/client instead.
3. kysely.destroy() should not be optional because users have no reason to call it otherwise.