Serve images in next-gen formats

Image formats like JPEG 2000, JPEG XR, and WebP often provide better compression than PNG or JPEG, which means faster downloads and less data consumption. Current .png and .jpg extensions in open library slow the loading of the site significantly almost 1.8s and there is an opportunity here to improve the page load speed.

**Pages:**

- [ ] Homepage

### Evidence / Screenshot (if possible)
#### Home Page delay:

### Relevant url?

https://developers.google.com/speed/pagespeed/insights/?url=openlibrary.org
[Link for efficiently encoding images](https://web.dev/uses-optimized-images/?utm_source=lighthouse&utm_medium=devtools)

### Stakeholders

@tabshaikh