support pc that doesn't have GPU

[oligamiq]

I think the smooth performance of applications using this library is really impressive.
By the way, do you have any plans to support running without a GPU?
I tried running it on a Windows PC without a GPU, but I encountered the following error:

thread 'main' panicked at C:\Users\oligami\.cargo\registry\src\index.crates.io-6f17d22bba15001f\wgpu-0.20.1\src\backend\wgpu_core.rs:751:18:
Error in Surface::configure: Validation Error

Caused by:
    Invalid surface

[DJMcNab]

We'd like to get that working, but it's not a priority for us at the moment.