Previously, zip.js and fflate were built from the main Foliate repo.
And PDF.js files were copied manually. Now they all build here.
Unfortunately, two CSS files still need to be copied manually.
The fixed-layout renderer now accepts an object for the return value of
`load()` (on the `book.sections` items). If it's an object, the `src`
is the URL of the section, and `onZoom`, if present, will be called
when the viewport is zoomed. With this you can scale the page yourself
rather than relying on the renderer's own scaling with CSS transform.
Also upgraded to PDF.js 4.6.82. And now internal links are broken...
Don't know how to fix that yet.