Add structured unknown error from telegram api

[ev-gusev]

There are cases when api telegram returns errors that do not have static text, for example:

Bad Request: can't parse entities: Can't find end tag corresponding to start tag "b"

In this case, it is impossible to determine on the library user side that this error is a Bad Request, as it will be generic and will only contain the error text

This PR solves this problem and allows to handle such errors as follows:

	var e *telebot.Error
	if errors.As(err, &e) {
		if e.Code == 400 {
			...
		}
	}

Errors that were previously predefined as bad request will be handled in the same form

[demget]

Hey @ev-gusev, good catch. I think we can change default case instead to generalize such conversion

[ev-gusev]

Hey @ev-gusev, good catch. I think we can change default case instead to generalize such conversion

I actually thought about it, but I thought that there might be library users who used regular expressions and parsed these errors that were not of type Error to accomplish the goals I was pursuing . So I didn't risk it

[ev-gusev]

@demget What do you think about it?

[demget]

@ev-gusev we will include this in the breaking V4 release

[ev-gusev]

@ev-gusev we will include this in the breaking V4 release

I got you, changed the default case