[Input] Better support required field

[oliviertassinari]

• Closes [TextField] Required TextField has a red border in Firefox #7887
• Reset Firefox style
• Fix some docs issues

Breaking change

Following Bootstrap, we are now forwarding the required property down to the input component. We used to only apply aria-required. This move makes us less opinionated and should help with native form handling.

If you want to avoid the default browser required property handling, you can add a noValidate property to the parent form.

• PR has tests / docs demo, and is linted.
• Commit and PR titles begin with [ComponentName], and are in imperative form: "[Component] Fix leaky abstraction".
• Description explains the issue / use-case resolved, and auto-closes the related issue(s) (http://tr.im/vFqem).

[oliviertassinari]

@rosskevin If you don't mind. I think that I will keep asking you a review on breaking changes PR 😁