Improve background + HDR

[madjin]

In order to make pbr materials look amazing, we should look into these improvements

• add hdr map
• add ability to change background texture + hdr

btw WebGPU HDR support is coming to threejs 170: mrdoob/three.js#29573

• https://developer.chrome.com/blog/new-in-webgpu-129

wont work on linux yet by default tho

[madjin]

    const hdr = new RGBELoader().load("./hdr/studio_small_09_2k.hdr", (hdr_) => {
        hdr_.mapping = THREE.EquirectangularReflectionMapping;
        scene.environment = hdr_;
        scene.background = hdr_;
    })

can patch this into sceneinitializer (thx @Benjythebee!)