Minor QOL improvement: Theme tab Apply and Reset buttons shouldn't require scrolling

The issue: When creating themes or playing with new ones, I need to hit "Apply" constantly. This usually just means that I have to change the theme and then scroll alllllll the way to the bottom to Apply.

Code: This doesn't add any new options, it just duplicates the Apply and Reset buttons to the bottom of the theme tab with CSS. This means I can change the theme and hit Apply with no unnecessary scrolling and UI travel. This... is good. It's needed. Please accept.

Screen (as shown running on npm run dev)