fix: default x y to 0 when not provided, accept 0 value

[amoshydra]

Note to maintainer: Feel free to modify on top of this PR

Summary

Accept 0 for x and y by checking if the value provided is falsey using == null.

   const position =
-    options.x && options.y
+    options.x == null && options.y == null
       ? { x: options.x, y: options.y }
       : options.touchPosition;

If either x or y is provided, prefill the undefined y or x with 0

   const position =
     options.x == null && options.y == null
-      ? { x: options.x, y: options.y }
+      ? { x: options.x || 0, y: options.y || 0 }
       : options.touchPosition;

This is necessary also as Position require both x and y to be defined:

https://github.com/amoshydra/cypress-real-events/blob/d2c3caa0b3ed73109db04b984d8257a0b653f3a1/src/getCypressElementCoordinates.ts#L1-L11

Related issue

This should resolve #641

Motivation

To allow realSwipe to start at x: 0, y: 0

[what-the-diff]

PR Summary

• Enhanced Handling for Position Variable in realSwipe Command
  In the realSwipe command, improvements have been made to accommodate scenarios where the x and y options are not assigned any value. This ensures the command performs consistently in varied use cases.