fix(TS): declare first parameter of screen.debug as optional (#573)

Author: simrobin

types/screen.d.ts

@@ -8,7 +8,7 @@ export type Screen<Q extends Queries = typeof queries> = BoundFunctions<Q> & {
      * of elements
      */
     debug: (
-        element: Element | HTMLDocument | Array<Element | HTMLDocument>,
+        element?: Element | HTMLDocument | Array<Element | HTMLDocument>,
         maxLength?: number,
         options?: OptionsReceived,
     ) => void;