A way to use mesh.split_to_u16() with egui_glow()

[justinturpin]

Is your feature request related to a problem? Please describe. Hello all, I've been on a quest to get this working with a Raspberry Pi 3b which only supports OpenGL ES 2.0 in an EGL context. Long story short, it only supports UNSIGNED_SHORT for the mesh indices, whereas egui_glow seems to be hardcoded with UNISIGNED_INT. Mesh supports split_to_u16() so I was able to fork off egui to add:

              Primitive::Mesh(mesh) => {
                    for mesh16 in mesh.clone().split_to_u16() {
                        self.paint_mesh16(&mesh16);
                    }
                }

to painter.rs. And then self.paint_mesh16() is the same as paint_mesh except it uses a glow::UNSIGNED_SHORT.

Describe the solution you'd like

Ideally egui_glow would support this automatically? Or possibly put it under some feature flag.

Describe alternatives you've considered

For now I can just keep a local fork going, this is just for a toy project anyways.

Additional context

Thank you for your time!

[emilk]

I guess this could be a flag during startup, if you feel like making a PR!