Buttons should support href as a prop

[jdrush89]

Describe the bug
According to #1972, LinkButtons have been removed in favor of <Button as="a" />. If this is the recommended way of doing link buttons, then passing an href to the Button component should forward that prop to the a element. Otherwise, an onClick that sets the window.location.href has to be used which is more code and clunkier.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://primer.style/react/Button
2. Update the first example to <Button as="a" href="http://google.com">Default</Button>
3. Click on the Button in the first example
   

Expected behavior
The user should be navigated to the url passed in as the href.

Desktop (please complete the following information):

• OS: Windows 10
• Browser chrome
• Version 101.0.4951.67 (Official Build) (32-bit)

[AdamShwert]

This bug also causes an issue where when you middle mouse click on a button, nothing happens because the href prop is not passed through. We are currently still using LinkButtons as a result so as to not lose functionality until this issue is resolved