SEP 58: Define asset transformations within manifest

Currently all images are compressed to a fixed ‘quality’ level, this works fine but in some cases (particularly if I’m including an image that has already been compressed/optimised) this results in double compression with a commensurate and needless drop in quality.

It would be useful to be able dictate how a given asset (eg image/video) is to be transformed during a site build. Initially I would implement for regular images, allowing both a new resolution and a level of compression to be specified in the manifest.

Should there be a default transformation set or should all transformations require explicit specification?