Test available backends for wgpu

Cargo.toml

[dependencies]
wgpu = "0.6.0"

test_wgpu_support.rs

use wgpu;

fn main() { 
    for &bit in [
        wgpu::BackendBit::DX11,
        wgpu::BackendBit::DX12,
        wgpu::BackendBit::GL,
        wgpu::BackendBit::VULKAN,
        wgpu::BackendBit::METAL,
        wgpu::BackendBit::PRIMARY,
        wgpu::BackendBit::SECONDARY,
        wgpu::BackendBit::BROWSER_WEBGPU,
    ].iter() {
        let instance = wgpu::Instance::new(bit);
        let av = instance.enumerate_adapters(bit);
        println!("backend: {:?}, detectes {} adapters", bit, av.count());
    }
}