mention load in texture class

doc/classes/Texture.xml

@@ -5,6 +5,7 @@
 	</brief_description>
 	<description>
 		A texture works by registering an image in the video hardware, which then can be used in 3D models or 2D [Sprite] or GUI [Control].
+		Textures are often created by loading them from a file. See [method @GDScript.load].
 	</description>
 	<tutorials>
 	</tutorials>