Accessibility: Set alt-text for cables <canvas> area as a patch setting

[TobyKLight]

Request is a field in Patch Settings menu that sets the alt-text for the cables.gl canvas. Use case is for making accessible patches when they are equivalent to an image and you can descibe their content in alt-text instead. (e.g a simple animated data vis)

(Note for a <canvas> tag alt text goes between the starting and closing </canvas> tags, unlike img alt text which uses an attribute)

[pandrr]

on dev.cables.gl we now have a innerHTML op, you can use this to set the innerText of the canvas to a value, that should solve it

in general: patch settings are more about the patch on cables.gl website. we need to solve those things in operators or cables core, otherwise they won't be in the standalone, or would not work with, e.g webgpu etc.

[steam0r]

this made it to cables.gl with the latest release, just now!