Primitive Mode TRIANGLE_STRIP and TRIANGLE_FAN

[atteneder]

The following glTF primitive modes are not implemented:

-TRIANGLE_STRIP
-TRIANGLE_FAN

Unity does not support those out of the box, so glTFast needs to generate indices (similar to how it creates them for missing indices on TRIANGLES mode primitives).

Unfortunately I've never encountered such a glTF file, so we'd have to find or create one first.

[Hexer611]

Chronos group has a glTF asset generator which should be useful as an example to implement these primitive modes.
Link: https://github.khronos.org/glTF-Asset-Generator/Output/Positive/Mesh_PrimitiveMode/

I would like to contribute to this project. Since this issue is tagged with "good first issue" I believe this is a good point to try it :D

Out of context note: The link to "code of conduct" in "https://github.com/atteneder/glTFast/blob/openupm/CONTRIBUTING.md" doesn't work, I could send a PR to fix that if possible :D

[atteneder]

@Hexer611 Thanks for going ahead and submitting PRs.

Regarding the incorrect linke: Sure, go ahead! Targetting the Unity fork is the way to go.

I'll look at your PR in 1-2 weeks.

Keep it up!