Docs: improve Promise typing

[s-rigaud]

Description

By Js standard Promise is a generic so not defining a type inside arrows ends up to be Promise<Any>. I just tried to improve the typing for some methods.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.52 79.1	339.52 79.1	+0 B +0 B
WebGPU	490.81 136.38	490.81 136.38	+0 B +0 B
WebGPU Nodes	490.27 136.28	490.27 136.28	+0 B +0 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	465.41 112.15	465.41 112.15	+0 B +0 B
WebGPU	561.38 152.09	561.38 152.09	+0 B +0 B
WebGPU Nodes	516.77 141.66	516.77 141.66	+0 B +0 B