update to bevy 0.13

[ThomasAlban]

I followed the migration guide to update this to bevy 0.13. However there is currently a WGPU error when you try to run it:

wgpu error: Validation Error

Caused by:
    In Device::create_render_pipeline
      note: label = `pbr_grid_shadow_pipeline`
    Error matching ShaderStages(VERTEX) shader requirements against the pipeline
    Shader global ResourceBinding { group: 1, binding: 0 } is not available in the pipeline layout
    Storage class Uniform doesn't match the shader Storage { access: StorageAccess(LOAD) }

I think this is due to the swapping of material and mesh bind groups in bevy 0.13, but I don't know enough about this to feel comfortable fiddling around with the numbers. Any help with that appreciated!