Proposal: Add .riv to application/zip

[XChikuX]

Context
The .riv file format is a ZIP container format for bundling Rive animations with their assets. It is widely used in React Native, Web, iOS, and Android apps for efficient animation packaging.

Currently, .riv is not recognized in mime-db. Most platforms fall back to treating it as a generic application/zip, which causes friction when serving these files over HTTP, e.g. missing correct headers, caching issues, or requiring vendor patches (as in our case).

What we propose
Map the .riv extension to application/zip in mime-db, alongside .zip.

"application/zip": {
"source": "iana",
"compressible": false,
"extensions": ["zip", "lottie"]
}

NOTE: I've copied over the proposal from #404 for lottie. It needs to be determined whether application/zip is correct mime type for *.riv files.

Importing lottie files through expo-assets now works with #351

We should quickly be able to make one with a similar PR as above.

Just waiting on someone from the RIVE repo to confirm the above mime type. rive-app/rive-react-native#241