skia-enabled ft2-demos with ot-svg suport, updated to m125 and now on github.

[Hin-Tak Leung]

I have set up a repo for the skia ot-svg patch, updated it for skia m125 (out 
two weeks ago; skia-python m124 was released last week and there is a pull for 
m125), and set up github CI to build it against current freetype git head.

https://github.com/HinTak/freetype2-demos-skia/

Documentation is a bit sparse (definitely missing a "requirement" section - 
read the CI yaml for what is needed), and the build scripts needs to be updated 
to fail properly on CI (issue 1).

This is a patch to build ft2demos to use skia + its built-in svg parser, or 
svg-native-viewer + cairo or skia, to render ot-svg, in addition to the 
current, which is via rsvg + cairo (which has some bugs).

The Makefile part of the patch has some harmless bits which is part of another 
add-on for COLRv1 I am too lazy to remove. (and is part of what I have myself 
https://github.com/FontVal-extras/binary-archive/  , Fontval-enhanced freetype 
+ ot-svg & COLRv1 -enhanced ft2demos).

I'll go add all the above to the README.md now :-).