Add more features

[CrazyboyQCD]

Closes #3

• More supported targets
• C API bindings
• Global cache for downloaded file

[DouglasDwyer]

Thank you for your contribution.

• Could we gate the bindings generation and bindgen dependency behind a feature flag? That way, libraries like wgpu (which don't need the extra C bindings) won't need to compile the bindgen dependency tree.
• Have you tested building on other targets? If not, no problem - they can go untested until somebody tries to use them lol - but I would be curious to know which other platforms we guarantee are working.
• I have added a few other small comments/questions about style. Let's address them before merging :)

[CrazyboyQCD]

• Could we gate the bindings generation and bindgen dependency behind a feature flag? That way, libraries like wgpu (which don't need the extra C bindings) won't need to compile the bindgen dependency tree.

Done.

• Have you tested building on other targets? If not, no problem - they can go untested until somebody tries to use them lol - but I would be curious to know which other platforms we guarantee are working.

I only tested with msvc but I believe this should work with all windows targets.

[DouglasDwyer]

This PR looks good on my end. Do you have any other concerns, or is this ready to merge?

[CrazyboyQCD]

No for now, should be ok to merge.

[DouglasDwyer]

Thanks for making this PR!