Implementing Skia OT-SVG hook bridge in ftinspect?

Hi Hin-Tak, Werner and other folks,

The recent posts from Hin-Tak provided us promising insights in 
implementing OT-SVG hook bridges in calling programs. I wonder if the 
current status of Skia hook is approriate for being incorporating into 
ftinspect. My considerations are:

- Maturity of bridge code (namely, skia-port.[ch]): Are they performing 
well enough for a (experimental) integration? Do they work stably across 
Skia versions? I'm seeing different patches for different Skia versions;

- Building Skia: Skia is built using tools (e.g. gn) completely 
different from what we're using for building ftinspect (CMake and 
Meson). I plan to not directly include the commands to build Skia into 
the ftinspect build system, but to ask user to provide Skia library 
paths. However, I'm concerned that Skia depends on (possibly another 
build of) freetype, which may cause conflict. Maybe Hin-Tak have some 
tips on handling this correctly?

If done, I plan to flag this feature as experimental and optional 
(default disabled, enable in build system). However, I may lack the 
resources and experise to test the code thoroughly, so I wonder if 
Hin-Tak could help.

BTW @Hin-Tak, The Qt6 support for ftinspect has almost completely not 
been worked on, I just wrote the conditional compilation (specifically, 
code about `QTextCodec`) because I learnt that `QTextCodec` was 
deprecated in Qt6, and that's the only part I've considered about Qt6. 
Therefore, further work is definitely required to ensure the whole 
program works on Qt6. Sorry for the confusion.

Best regards,
Charlie Jiang