Complete UI overhaul

Concept

My team and I have been working hard on completely overhauling Courier's UI. This is done by introducing a new design system, tokens, brand, style, light and dark modes, UX, the list goes on 😂. First we will re-skin the app with our new components, then re-structure them to improve upon the experience, and finally re-build section by section to make it faster, lightweight, and generally more delightful.

Here is an enterprise version of our main menu in light and dark mode.