core: examples: add a few more WebGPU examples

[emidoots]

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: #227

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

[johanfforsberg]

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

[emidoots]

#410 brings the image-blur example

[alichraghi]

map-async added with #414

[alichraghi]

helloTriangleMSAA has been added with #513