DEV: Build/port new splash/info screens

[actuallydan]

If we npm run build:web and deployed it to AWS it would be significantly lacking in landing page functionality, which is pretty solid I'd argue. It'd be nice to have something, at least on the web, to act as a splash page.

Also, static or otherwise, the FAQs, roadmap and 404 pages should be ported over to the /web directory. These can just be static pages or routes, but they shouldn't(?) appear in the app in iOS or Android.

[actuallydan]

My plan for this is to copy all the pages -> components as near as possible from the existing site, where each page will be a screen, and will be optionally included

// ...routes
{ Platform.OS === 'web' &&
(
<Screen name='splash'/>
<Screen name='about'/>
<Screen name='404'/>
... more optional routes
)}

Convert the components to be use existing ones where possible. Additionally, set the default route (presumably whatever route is at the top) to be the splash page (should be ignored automatically if they plugged in a different route).

Acceptance Criteria:

• convert default route (channels) to "/app"
• on navigation to "/" on the web, the user should see the athar.es splash screen
• on nav to "/app" on web user should see channels and default news (if not mobile)
• on nav to "/" in native app...shouldn't happen, default to "/app"
• on navigation to any app route, regardless of platform or logged in state, user should be taken to screen with its own logic
• include "about" route
• include "roadmap" route