Added new Community List page to the login flow

[JakeShirley]

Addresses #78

Checklist

• [x] I have described what this PR contains

Choose one of the following two options:

• • [ ] This PR does not introduce major changes
• • [x] This PR introduces major changes, and I have consulted @buresdv, @jboi or @mormaer in the Mlem Development Matrix room

Choose one of the following two options:

• • [ ] This PR does not change the UI in any way
• • [x] This PR adds new UI elements / changes the UI, and I have attached pictures or videos of the new / changed UI elements

Pull Request Information

About this Pull Request

The PR add an Apollo-like communities screen. It is injected between the "Accounts" screen and the "Community View". This is a natural "home" screen that allows people to select what they want to browse when they first get into the app.

I am brand new to Swift and SwiftUI so please bear with me!

Screenshots and Videos

Video demo: https://www.youtube.com/watch?v=R52NyvqnBug

Additional Context

Still LOTS of clean up to do. Still learning the ropes and seeing where I can make re-usable components and what not.

I wrong a bunch of (ugly) code to generate samples for the SwiftUI preview to function (yay!). I rebased today (6/18) and had to disable a project setting for code coverage to get previews to work again (found the solution here).

[ShadowJonathan]

@buresdv why was this closed?

[JakeShirley]

PR is ready! Moved some views out into their own files and cleaned up the UI a little bit. Here it is:

[wi-ry]

Looks great @JakeShirley !

[buresdv]

I can't approve this in the current state. Will give more info when out of hospital