Docs: Improve Color page.

[Mugen87]

Fixed #25571.

Description

Adds getRGB() to the Color docs.

[Mugen87]

@donmccurdy When the colorSpace parameter was added in #23392, only the signature of the Color methods were updated in the docs. The parameter itself has no description. For example getHSL() is currently documented like so:

three.js/docs/api/en/math/Color.html

Lines 174 to 176 in 355ce7c

	<h3>[method:Object getHSL]( [param:Object target], [param:string colorSpace] = LinearSRGBColorSpace )</h3>
	<p>
	[page:Object target] — the result will be copied into this Object. Adds h, s and l keys to the object (if not already present).<br /><br />

But it should be something like:

<h3>[method:Object getHSL]( [param:Object target], [param:string colorSpace] = LinearSRGBColorSpace )</h3> 
 <p> 
 	[page:Object target] — the result will be copied into this Object. Adds h, s and l keys to the object (if not already present).<br />
 	[page:String colorSpace] — ???. Default is `LinearSRGBColorSpace`.<br /><br />

How should we document colorSpace?