examples: More WebGPU examples

I'd like to end up with most interesting WebGPU examples out there ported over for people to easily use/consume from Zig.

If you'd like to port one of these examples over (or come up with your own WebGPU example), feel free to do so and send a PR / post here! This is a tracking issue for exactly that.

You can use this as a template for where to put the code: https://github.com/hexops/mach/pull/227

• Examples we should port over from https://github.com/austinEng/webgpu-samples/tree/main/src/sample:
  • [x] boids
  • [ ] deferredRendering
  • [x] fractalCube
  • [x] helloTriangleMSAA
  • [x] imageBlur
  • [x] instancedCube
  • [ ] particles
  • [ ] reversedZ
  • [x] rotatingCube
  • [ ] shadowMapping
  • [x] texturedCube
  • [x] twoCubes
• Many from https://github.com/samdauwe/webgpu-native-examples can be ported over, too.

Guess we can check off the "instancedCube" box due to #246. Also there is a "two-cubes" example already.

https://github.com/hexops/mach/pull/410 brings the image-blur example

map-async added with #414

helloTriangleMSAA has been added with #513