dillon1000/react

JSXNamespacedName support

This is kind of a hack, but i think it's worth it given that JSXNamespacedName 
is relatively uncommon. Adding a new InstructionValue variant to represent a 
namespaced name is one option, but then that isn't a valid expression and can't 
appear as an operand anywhere else. Instead, we lower namespaced names as a 
primitive (string) as `${namespace}:${name}` — exploiting the fact the namespace 
and name can't have a colon, and non-namespaced tagnames also can't have colons. 

It's a bit of a hack but it's contained to the JSX processing code. If folks 
have strong opinions on this i'm happy to change but this felt reasonable as a 
quick and reliable way to unblock support. 

NOTE: there is a larger question of what to do about compiling `fbt` tags. 
Before we can do anything with them, though, we need to parse them.