`<input>` `[autocomplete]` `[min]` `[max]` `[step]`: implement validation

All these attributes change behavior based on the value of the `type` attribute of `<input>`.
Some types are just simple numbers that need to be parsed, but in some other cases more ad-hoc parsers need to be created.

Related links:
https://html.spec.whatwg.org/multipage/input.html#the-input-element
