feat: add support for custom input attributes

[AlexCLeduc]

Will keep this in a branch/rc-release until I confirm it helps solve our a11y testing

• add docs for input_attrs

Not super happy with this API. using the standard Widget attrs API would be nice but

• there may be other elements than the input whose attributes we may want to modify. I could see us adding more attributes like, chip_attributes, selected_ul_attributes, selected_li_attributes, etc. . After a certain point, though, we should just let people render things themselves, somehow.
• It may also break existing behavior as consumers may be passing attributes now that are getting ignored