Adding support for High Dynamic Range (HDR) imagery to HTML Canvas: a baseline proposal

The [Color on the Web CG](https://www.w3.org/community/colorweb/) would very much appreciate your feedback on the following strawman, which motivates and proposes baseline modifications to the HTML Canvas API to enable support for High-Dynamic Range (HDR) imagery:

https://github.com/w3c/ColorWeb-CG/blob/8eac62f15e5b41940636beb031f6214b61e933af/hdr_html_canvas_element.md

The proposed modifications allow the HTML Canvas API to manipulate High Dynamic Range (HDR) images expressed using the widespread BT.2100 PQ and BT.2100 HLG color spaces, without precluding adding future HDR capabilities, such as support for additional color spaces like a linear high-dynamic range color space.

Start by reading the linked ColorWeb-CG proposal, hdr_html_canvas_element.md, and compare its suggested HTML Canvas API changes with the existing WebGL project scope. Done would mean producing feedback on the baseline HDR approach, including BT.2100 PQ and HLG support and future color-space considerations.

Written by the indexing model from the issue text.