Correctly serialize radio buttons/checkboxes
Correctly serialize radio buttons/checkboxes

This is for `data-submitsend` support.

It turns out, `element.value` does correctly serialize <select> elements.

Fixes #1769

Zarel/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client