This moves github.com/hexops/mach-gpu@528dad0823dafeae5d474c88cc658b091bf2e605 to
this repository in the src/gpu directory. It can be imported via `@import("mach").gpu`.
Soon we will move away from mach-gpu entirely as part of #1166 - but in the meantime
I am giving a workshop at https://sycl.it and it would be nice for people using the
`mach.gpu.*` API to be able to search the API in this single repository.
There's not much harm to moving this code here.
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>