[Qt-creator] QtCreator Markdown Plugin

[Andrzej Telszewski]

Hi,

please have a look at:

- [ghostwriter](https://github.com/wereturtle/ghostwriter)
- [mindforger](https://github.com/dvorka/mindforger)

I'm actively using [ghostwriter] 1.8.1.

My point is that both projects provide navigation/sync between `#` 
headers, .md source and the HTML preview.
They use _Qt's WebEngine_ if I recall correctly, but as mentioned 
before, this could be switched to _qlitehtml_.

Could [cmark-gfm](https://github.com/github/cmark-gfm) be the answer for 
a C/C++ parser for Markdown?
I see it's not been updated since > 1 year, but the real question is 
whether there are any security issues needing _immediate_ treatment.

It is **REALLY** cool to see Markdown support landing in QtC.
Thank you for the effort!

--
Best regards,
Andrzej Telszewski