Create a demo page for all of the various UI elements

[jaohara]

Probably should use App.jsx for a dev preview of the components.

Should also have the following functionality:

• Light/dark mode toggle
• Style toggle for UI elements (visual style like solid button or border button)
• Change primary element color (highlight for button bg, links, etc)
• Toggle disabled state for elements
• Toggle "loading" or "busy" state for elements (buttons?)

[jaohara]

The Dev page currently displays all components outside of the Panes/Notifications.

The options for toggling light/dark mode/etc still need to be built, and should be blocked out so I don't forget about them.

[jaohara]

Light/Dark toggle has been implemented