Button: add focus() method

[Sole-Valero]

Steps

It is not possible to call focus() method when you hav a ref to an Button component
<Button ref={(button) => this.buttonRef=button} >Select All

This is a similar issue also solved for Input component:
#1475

Expected Result

this.buttonRef.focus() --> send the focus to the button

Actual Result

Uncaught TypeError:this.buttonRef.focus is not a function

[levithomason]

I think focusing a Button is common enough that this makes sense to implement this. Thanks for the idea.

In the meantime, here's a workaround:

const $button = document.querySelector('#my-button')
if ($button) $button.focus()

<Button id='my-button' />