Mozilla and Google both found SPIRV-Cross to be insufficient and built Naga and
Tint, respectively, so there's no need to support this build option.
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
It's nicer to refer to this in code as `gpu`. Additionally, `webgpu` as a name
gives the impression this is for web only which is absolutely not true but could
understandably be very confusing to newcomers.
Solve both problems by renaming to just `gpu`, and (next) updating the README to
indicate what it does and why, then explain it's WebGPU after as more of an
implementation detail.
Signed-off-by: Stephen Gutekanst <stephen@hexops.com>
