GLTFLoader: Pre-compute geometry bounds using attribute min/max

Instead of relying on three.js to compute bounding box/sphere, we now
compute them from attribute min/max specified in glTF file. These are
mandatory as per glTF spec.

This allows us to save time after loading the object - bounding sphere
is used for culling unconditionally.

Note that since glTF data doesn't directly specify bounding sphere data,
the bounding sphere is slightly larger because it's computed from min/max
values.

Use MeshStandardMaterial for displacement in panoramic 6DoF example

LoadingManager: Make .getHandler() more robust.

TS: Fix BufferGeometry.d.ts Plane.d.ts

Examples: Added panoramic 6DOF example 🌐

Implement support for KHR_mesh_quantization

TS: Clean up for single quote.

TS: Added missing multiView files.

TS: Clean up.

TS: Fix import in InstancedMesh.d.ts.

This change implements support for KHR_mesh_quantization by simply
recognizing the extension as supported. It seems that the extension
works otherwise after various quantization fixes submitted previously
(with the most recent fix including correct morph target handling for
deltas that are quantized with a different data type vs baseline
attribute).

PMREMGenerator: properly dispose of shader

DRACOLoader: Fix example decoder path.

LOD: Honor .autoUpdate in toJSON().

LOD: Make methods more robust.

EXRLoader: Clean up

Examples: Support drag-and-drop for EXR files in MatCap example

EXRLoader: RLE support and uncompress refactor.