Fix incorrect example in the documentation for the expand method in Rect2

[HexagonNico]

The documentation for the expand method in the Rect2 class currently contains this example:

var rect = Rect2(0, 0, 5, 2)

rect = rect.expand(Vector2(10, 0)) # rect is Rect2(0, 0, 10, 2)
rect = rect.expand(Vector2(-5, 5)) # rect is Rect2(-5, 0, 10, 5)

However, running the following code

var rect = Rect2(0, 0, 5, 2)

rect = rect.expand(Vector2(10, 0))
print(rect)
rect = rect.expand(Vector2(-5, 5))
print(rect)

produces this output:

[P: (0, 0), S: (10, 2)]
[P: (-5, 0), S: (15, 5)]

After the second call the rectangle becomes (-5, 0, 15, 5) instead of (-5, 0, 10, 5) because the first call modifies the rect variable, while the example assumes that the expand function is still called on the original rectangle.

Changing the example to

var rect = Rect2(0, 0, 5, 2)

var rect1 = rect.expand(Vector2(10, 0)) # rect1 is Rect2(0, 0, 10, 2)
var rect2 = rect.expand(Vector2(-5, 5)) # rect2 is Rect2(-5, 0, 10, 5)

should make it clear that the initial rectangle is still the same.

[AThousandShips]

I'd suggest just fixing the incorrect results instead of changing the example

[HexagonNico]

I've changed the example to

var rect = Rect2(0, 0, 5, 2)

rect = rect.expand(Vector2(10, 0)) # rect is Rect2(0, 0, 10, 2)
rect = rect.expand(Vector2(-5, 5)) # rect is Rect2(-5, 0, 15, 5)

[akien-mga]

Thanks!