fix: Add new shadowIntensity value to mtoon shader

[ashconnell]

Three 166 introduces a new light.shadowIntensity value (mrdoob/three.js#28588) which breaks three-vrm as the shader won't compile.

This PR updates the MToon fragment shader to use the new value.

[0b5vr]

@ashconnell Thank you for the contribution!

We usually provide broader compatibility against past Three.js versions, so compat codes are mandatory in MToon shader codes.
Would you add a compat code following the code example below?
You would probably use the expression THREE_VRM_THREE_VERSION >= 166.

three-vrm/packages/three-vrm-materials-mtoon/src/shaders/mtoon.frag

Lines 653 to 660 in 9e16c38

	// COMPAT: pre-r156 uses a struct GeometricContext
	#if THREE_VRM_THREE_REVISION >= 157
	getPointLightInfo( pointLight, geometryPosition, directLight );
	#elif THREE_VRM_THREE_REVISION >= 132
	getPointLightInfo( pointLight, geometry, directLight );
	#else
	getPointDirectLightIrradiance( pointLight, geometry, directLight );
	#endif

After changing the code, please make sure that the code is working correctly on both r165 and r166.

[0b5vr]

@ashconnell Hello, could you make the change I mentioned above?

[0b5vr]

Superseded by #1441