refs #5652, #5719
- adds a timeout to `gh-spin-button` so the spinner is always shown for at least 1 second
As a stopgap solution before #5719 can be implemented it was decided to keep the button spinning for a minimum time, even if the associated action completes quickly. Discussion can be found at https://ghost.slack.com/archives/dev/p1440670418004358
refs #5652
- ensure gh-spin-button passes type & tabindex through to markup
- add gh-input class to auto focus input
- add tabindexes to setup/two + make first field autofocus and button submit
