HDR / wide color gamut support

**Is your feature request related to a problem? Please describe.**
Upcoming image formats for browsers (avif) will have support HDR /wide color gamut.
CanvasRenderingContext2d currently does not.
This suggests possible issues with regards to HDR support:
* what should happen to the HDR/gamut data when converting to formats that don't support it?
* what should happen to the HDR/gamut data when resizing an avif file?

**Describe the solution you'd like**
* [ ] figuring out how to handle import of HDR/gamut data
* [ ] figuring out how to handle export of HDR/gamut data
* [ ] development of general policy on how to handle features that image formats support but browsers don't provide native APIs for
* [ ] figure out if it's out-of-scope or not to *add* HDR/gamut data when manipulating an image in circumstances where squoosh transformations may benefit from doing so.

**Additional context**
* whatwg/html#4167

No repository file or test is named. Start by reading WHATWG/html#4167 and tracing the CanvasRenderingContext2d paths involved in AVIF import, export, and resizing. Define how HDR and wide-gamut data should be handled, including whether adding it is in scope; done means these policy questions have an agreed implementation scope.

Written by the indexing model from the issue text.