Add `uv_transform` to `ColorMaterial`

[rparrett]

Bevy version

main

What you did

Users want to do repeating textures on 2d meshes.

What went wrong

The helper we provide for doing that in 3d doesn't exist on 2d materials.

See the repeated_texture examples and docs for StandardMaterial::uv_transform

I think we should add a similar field to ColorMaterial for 2d users.

Additional information

Users can also accomplish tiling textures with SpriteImageMode, but that only works for sprites, not Mesh2d.

Alternatives

A helper on Mesh or RectangleMeshBuilder for transforming UVs?