Document creating Texture2DArray, Cubemap and CubemapArray from code

doc/classes/Cubemap.xml

@@ -6,7 +6,8 @@
 	<description>
 		A cubemap is made of 6 textures organized in layers. They are typically used for faking reflections in 3D rendering (see [ReflectionProbe]). It can be used to make an object look as if it's reflecting its surroundings. This usually delivers much better performance than other reflection methods.
 		This resource is typically used as a uniform in custom shaders. Few core Godot methods make use of [Cubemap] resources.
-		To create such a texture file yourself, reimport your image files using the Godot Editor import presets. The expected image order is X+, X-, Y+, Y-, Z+, Z- (in Godot's coordinate system, so Y+ is "up" and Z- is "forward"). You can use one of the following templates as a base:
+		To create such a texture file yourself, reimport your image files using the Godot Editor import presets. To create a Cubemap from code, use [method ImageTextureLayered.create_from_images] on an instance of the Cubemap class.
+		The expected image order is X+, X-, Y+, Y-, Z+, Z- (in Godot's coordinate system, so Y+ is "up" and Z- is "forward"). You can use one of the following templates as a base:
 		- [url=https://raw.githubusercontent.com/godotengine/godot-docs/master/tutorials/assets_pipeline/img/cubemap_template_2x3.webp]2×3 cubemap template (default layout option)[/url]
 		- [url=https://raw.githubusercontent.com/godotengine/godot-docs/master/tutorials/assets_pipeline/img/cubemap_template_3x2.webp]3×2 cubemap template[/url]
 		- [url=https://raw.githubusercontent.com/godotengine/godot-docs/master/tutorials/assets_pipeline/img/cubemap_template_1x6.webp]1×6 cubemap template[/url]