Add default arguments

[Sainan]

I know that only 3 4 natives having this new attribute isn't gonna the most impressive start, but I'm hoping that in the long run, this will help simplify usage of natives:

• Make it easier to call certain natives, e.g. SET_ENTITY_HEALTH's p2 will pretty much always be 0, no need to specify it explicitly.
• Make it easier to upgrade to newer natives versions, e.g. if there's a new p2 or p3 it can just be defaulted to 0, so it has exactly the same value as it did before.

Interoperability considerations:

• The "default" field matches https://github.com/DottieDot/GTAV-NativeDB/blob/master/special-schema.json except I've also restricted the possible values to make it easier for users of the nativedb to filter this value.