Make flatmesh GLES2/3 compatible

[zeyus]

This prevents errors about "#version" being unrecognized, and breaking shader compilation on devices that don't support GLES3

[zeyus]

Made draft because there is an issue with indices on GLES2

[MagneFire]

I'm working on a fix too, it's here: https://github.com/MagneFire/qml-asteroid/commits/fix/flatmesh-gles2.0/

Basically moves the logic from GPU to CPU. But I'm still cleaning it up and then haveto make it work on non-GLES 2.0.

[zeyus]

@MagneFire well no doubt whatever solution you come up with will be better, I don't have much experience in this domain (apart from more general playing with shaders and some graphics/canvas rendering for WebGL, flutter/flame, etc), but this as-is, now works on my mooneye watch, i can finally use the UI, open settings etc.

if there's anything here that's useful, feel free to take it, and bring it into your branch and we can close this whenever.

[MagneFire]

My preferred solution would be an all on GPU one but that seems a bit hard to achieve. I haven't had a look at your changes. It's entirely possible that your changes are better.

[zeyus]

My preferred solution would be an all on GPU one but that seems a bit hard to achieve. I haven't had a look at your changes. It's entirely possible that your changes are better.

Haha kind of you, but I think the flat shading might be missed (I honestly don't mind my watch is so old that it has a sun dial burnt into the OLED)