Add mapping for libctru GPU enums

[lrk]

Hi,

I wrote rust mapping for libctru/include/3ds/gpu/enums.h minus those already mapped in citro3d-rs because I may need them for my own projet.

Being new to citro3d-rs and having small experience with rust, please point out enums already mapped that i missed or unmet contributing standards.

Thx.

[lrk]

@ian-h-chamberlain Hi, not sure how you choose reviewers here, but since you seem to be the one who contribute the most, I ping you.

[ian-h-chamberlain]

@ian-h-chamberlain Hi, not sure how you choose reviewers here, but since you seem to be the one who contribute the most, I ping you.

Apologies, I've been a bit inactive lately but I'm trying to get through my backlog of Github notifications now 😅

First thing I'll say: I'm not sure whether this crate should be providing wrappers around ctru_sys types... I would expect ctru to wrap ctru-sys and citro3d to wrap citro3d-sys. But maybe that's it's a good idea to deprecate some of these ctru-sys bindings entirely and move them here instead, then do something like this PR (and I don't think there's any harm in generating them in both places).

I also wonder if we might be able to get bindgen to do a lot of the work for us here, instead of having to maintain hand-written types like these.

I haven't yet had a chance to look through all of this, but let me look into what options bindgen gives us (and think about migrating a bunch of these over to citro3d from ctru).