webp support - at least preserve the filename...

ok so a few problems.

firstly, webp isn't actually supported - discord converts it to png, which, ironically, makes the file size waaaay bigger since png is lossless. for example, when i post a ~3mb webp it turns into a ~40mb png... no thanks. it's supported by all major browsers with the exception of safari on macos <11 apparently. not to mention if it was an issue, users could just... not post webps? https://caniuse.com/webp 

more importantly, after the conversion, the file name is lost. it's more than a bit frustrating when there is important info in the file name and it just becomes "unknown.png"