Add autocapitalize="off" on form

This global attribute [1] instructs the user agent to not
auto-capitalize input on some input methods – that is, for example, a
virtual, on-screen keyboard will not start with an uppercase letter, but
rather with a lowercase one. Thanks to User:Waldir for the tip!

[1]: https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autocapitalize