docs: Document mouse outside screen (solves #651)

Author: JerwuQu

site/docs/guides/user-input.md

@@ -404,8 +404,8 @@ export fn update() void {
 
 ## Mouse
 
-Mouse (or touchscreen) input is supported. See the [Memory Map](/docs/reference/memory)
-reference for more details on `MOUSE_X`, `MOUSE_Y`, and `MOUSE_BUTTONS`.
+Mouse (or touchscreen) input is supported and will work for positions even outside of the game window on supported platforms.
+See the [Memory Map](/docs/reference/memory) reference for more details on `MOUSE_X`, `MOUSE_Y`, and `MOUSE_BUTTONS`.
 
 On the example below, we can make a rectangle follow the mouse position and expand when clicked:
 

site/docs/reference/memory.md

@@ -82,11 +82,11 @@ Example:
 
 ### MOUSE_X
 
-Signed 16 bit integer containing the X position of the mouse.
+Signed 16 bit integer containing the X position of the mouse. Can contain positions outside of the game window.
 
 ### MOUSE_Y
 
-Signed 16 bit integer containing the Y position of the mouse.
+Signed 16 bit integer containing the Y position of the mouse. Can contain positions outside of the game window.
 
 ### MOUSE_BUTTONS