Add CustomToneMapping to the documentation (#24419)

* Update Renderer.html

* Update Renderer.html

* Update Renderer.html

Slightly rephrase tone mapping description.

Co-authored-by: Michael Herzog <[email protected]>

docs/api/en/constants/Renderer.html

@@ -46,14 +46,17 @@
 		THREE.ReinhardToneMapping
 		THREE.CineonToneMapping
 		THREE.ACESFilmicToneMapping
+		THREE.CustomToneMapping
 		</code>
 		<p>
 		These define the WebGLRenderer's [page:WebGLRenderer.toneMapping toneMapping] property.
 		This is used to approximate the appearance of high dynamic range (HDR) on the
-		low dynamic range medium of a standard computer monitor or mobile device's screen.<br /><br />
-
+		low dynamic range medium of a standard computer monitor or mobile device's screen.
+		</p>
+		<p>
+		THREE.LinearToneMapping, THREE.ReinhardToneMapping, THREE.CineonToneMapping and THREE.ACESFilmicToneMapping are built-in implementations of tone mapping.
+		THREE.CustomToneMapping expects a custom implementation by modyfing GLSL code of the material's fragment shader.   
 		See the [example:webgl_tonemapping WebGL / tonemapping] example.
-
 		</p>