Add SphereicalHarmonics3.d.ts

src/math/SphericalHarmonics3.d.ts

+import { Vector3 } from './Vector3.js';
+
+export class SphericalHarmonics3 {
+	constructor();
+
+	coefficients: Vector3[];
+	isSphericalHarmonics3: boolean;
+
+	set (coefficients: Vector3[]): SphericalHarmonics3;
+	zero(): SphericalHarmonics3;
+	add(sh: SphericalHarmonics3): SphericalHarmonics3;
+	scale(s: number): SphericalHarmonics3;
+	lerp(sh: SphericalHarmonics3, alpha: number): SphericalHarmonics3;
+	equals(sh: SphericalHarmonics3): boolean;
+	copy(sh: SphericalHarmonics3): SphericalHarmonics3;
+	clone(): SphericalHarmonics3;
+	fromArray(array: number[]): SphericalHarmonics3;
+	toArray(): number[];
+
+	static getBasisAt(normal: Vector3, shBasis: number[]): void;
+};