Add an example on iterating an array backwards

This closes godotengine/godot-docs#3472.

(cherry picked from commit 810d8f0)

modules/gdscript/doc_classes/@GDScript.xml

@@ -833,7 +833,8 @@
 		<method name="range" qualifiers="vararg">
 			<return type="Array" />
 			<description>
-				Returns an array with the given range. Range can be 1 argument N (0 to N-1), two arguments (initial, final-1) or three arguments (initial, final-1, increment).
+				Returns an array with the given range. Range can be 1 argument [code]N[/code] (0 to [code]N[/code] - 1), two arguments ([code]initial[/code], [code]final - 1[/code]) or three arguments ([code]initial[/code], [code]final - 1[/code], [code]increment[/code]). Returns an empty array if the range isn't valid (e.g. [code]range(2, 5, -1)[/code] or [code]range(5, 5, 1)[/code]).
+				Returns an array with the given range. [code]range()[/code] can have 1 argument N ([code]0[/code] to [code]N - 1[/code]), two arguments ([code]initial[/code], [code]final - 1[/code]) or three arguments ([code]initial[/code], [code]final - 1[/code], [code]increment[/code]). [code]increment[/code] can be negative. If [code]increment[/code] is negative, [code]final - 1[/code] will become [code]final + 1[/code]. Also, the initial value must be greater than the final value for the loop to run.
 				[codeblock]
 				print(range(4))
 				print(range(2, 5))
@@ -845,6 +846,20 @@
 				[2, 3, 4]
 				[0, 2, 4]
 				[/codeblock]
+				To iterate over an [Array] backwards, use:
+				[codeblock]
+				var array = [3, 6, 9]
+				var i := array.size() - 1
+				while i &gt;= 0:
+				    print(array[i])
+				    i -= 1
+				[/codeblock]
+				Output:
+				[codeblock]
+				9
+				6
+				3
+				[/codeblock]
 			</description>
 		</method>
 		<method name="range_lerp">