Using the user agents capabilities for loading images on web

[valaphee]

Is your feature request related to a problem? Please describe.
There is no need for a full-on image parsing library on wasm builds, as the user agent integrates plenty of image parser. It's also possible to directly initialize images from such sources. Either through HTMLImageElement or ImageData.

This would improve the loading times, by removing the image parser running in wasm, and the delivery time of the wasm file itself, as the image crate itself is quite heavy.

Describe the solution you'd like

Switching over to using HTMLImageElement.

Describe alternatives you've considered

Additional context
Depends on gfx-rs/wgpu#5668