docs: update setErrorHandler to explain not found behaviour

[domdomegg]

Coming from other frameworks this is somewhat surprising. This documents the behaviour and explains to catch 404 errors users need to set a not found handler.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[Fdawgs]

Probably doesn't need to be a note. Just incorporate it into the original paragraph.

[domdomegg]

Probably doesn't need to be a note. Just incorporate it into the original paragraph.

Is there guidance on when we should / shouldn't use notes? Seems unclear why this would be different to the note about being in a onResponse hook.

Happy to make the change - just wondering whether I should also change that too.

[Fdawgs]

Is there guidance on when we should / shouldn't use notes? Seems unclear why this would be different to the note about being in a onResponse hook.

Not yet, it's something I plan on reviewing next year as the number of note blocks is getting a bit excessive in some parts. And if we're needing all these notes then it means the original documentation wasn't clear enough in the first place. 😊

[domdomegg]

Sure, I've updated this section to remove the note blocks. Given these are both exceptions to what setErrorHandler processes, rather than repeat the same wording twice I've put them into a combined bullet list.