Support error handler middlewares

[leonardoraele]

This PR adds support for error handler middlewares in express-style syntax.

Notes:

• Since hyperbun only accepts registering a single middleware at a time, it might make sense to have them being registered with a different method than .middleware() (which this PR does't cover) instead of assuming based on the amount of parameters.
• This PR is a draft and was not tested yet. There's probably typescript issues in there that still need to be addressed.