UX: change tabindex on login to skip email login link (PR #14732)

Some discussion here: TAB at login styling - ux - Discourse Meta

This changes the tabindex of elements so the “Skip the password; email me a login link” link that shows under the username input doesn’t interrupt the usernamepassword tab order that keyboard users and autofill extensions have come to expect.

Visually the “Skip the password; email me a login link” under the username input is the “right place, right time” for users that aren’t navigating with their keyboard… so using tabindex is a compromise.

GitHub