Redo of the SVG Accessibility Appendix

Here is the first rewrite in the editors draft. It highlights the need to
produce revised Accessibility authoring guidelines document when we are
ready.

https://svgwg.org/svg2-draft/access.html

All the old SVG references are out and we can now reference our
Accessibility API Mapping specifications. I will also reference the HTML
accessibility mapping specification when the FPWD gets published as our use
of the canvas element requires results in descendant HTML content for
fallback. It is now out for review.




Rich Schwerdtfeger