Discussion of more standard interface between Canvas and wxWidgets

Inspired by the PR in lunasvg sbumitted by @chearon, I converted one of my test repositories to public and created a discussion area: https://github.com/Randalphwa/lunasvg-tests/discussions/20

Current plans are for wxWidgets to move from a dev release to a final release in Q1 of 2027, so ideally any changes to the wxWidgets side of lunasvg support should be done this fall while the interface is still open. After the final release, backwards compatibility will need to be maintained going forward.