Missing/more errors

Thanks for this great library, it's fantastic to be able to query directly from Cloudflare Pages 🥳

Based on my experiments so far I feel like the library is pretty silent regarding errors, instead of returning or throwing anything it just does nothing, for example inserting a record with an existing id twice, only the first time shows the result of the query, second time nothing happens.

Personally I definitely prefer that it doesn't throw but it'd be really helpful if it could return errors, so I could react accordingly.

const result = await conn.execute(`INSERT INTO user (id, username) VALUES (?, ?)`, [id, username]);
console.log(JSON.stringify({ result }, null, 4));

Edit: just stumbled upon https://github.com/planetscale/database-js/pull/62 😅 though as stated I'd prefer the former returning errors instead of throwing, or the option to configure this, in my case it does nothing where I expect some form of information.

Start by reproducing the INSERT behavior through conn.execute and read the discussion in pull request #62, which the issue references. Compare the requested returned-error behavior with the existing throwing behavior and define a consistent result or configuration contract; done means duplicate-record errors are observable and covered by the project's tests.