Focus in code input when totp is checked

[thrijith]

What?

This PR updates the UX for when TOTP is checked it focuses in the code input, fixes #159

Why?

For better UX as requested in #159

How?

Adds an event listener to check when the checkbox is enabled to focus into the code.

Testing Instructions

Start the env after checking out into the branch go to http://localhost:8888/wp-admin/profile.php, scroll down two factor options, confirm it focuses into the input.

Screenshots or screencast

https://share.cleanshot.com/qWNlb6gQTp90hDS8Fq0Q

Changelog Entry

Changed - UX update, focus into code input when TOTP is enabled

[kasparsd]

This looks good! Can switch to jQuery for consistency with the rest of the inline JS in a follow-up pull request.

Also, need to ensure that this JS doesn't fail if the TOTP method is not available (disabled via code, for example).