Astro rfcs

Components
- <Raw/> escaped-and-raw-components
- <Escape/> escaped-and-raw-components
Compiler
- AllowedCustomElements custom-elements
API
- Astro.defer(execute: function,point: number = 1)
  - Runs after rest of site is built
    - Site.0
    - Astro.defer.1
    - Astro.defer.2
    - Astro.defer.2
    - Astro.defer.3
    - etc
- Astro.compile(thing: function) run at compile time, entire Astro.compile(...) is replaced with whatever thing returns (let n = Astro.compile(function() {return 5 + 5}) is compiled into let n = 10 once built)