Please add an example of using GDI+ backend

[Fuckoffee]

[snuk182]

The original Nuklear has a GDI+ demo. Need to merge it with backend-less example, utilizing the raw winapi bindings + extract a GDI+ backend then. Will see how fast I can do this!
Also Windows subsystem support may influence.

[snuk182]

While there is no GDI+ bindings (for objective reasons), would GDI backend be reasonable?

[Fuckoffee]

I think that GDI or Direct2D will be a good backend

[snuk182]

Done with https://github.com/snuk182/nuklear-backend-gdi .
Sample https://github.com/snuk182/nuklear-test/tree/gdi .