Added an add at position subroutiune to linked list (#9020)

* added addAtPosition to simple linked list

* added addAtPosition to simple linked list

* modified the add function to take an optional position command

* fixed type safety errors:

* fixed type safety errors:

* fixed type safety errors:

* fixed type safety errors:

* fixed size error

* fixed size error

* added doctest and updates the else after checking if posiiton argument less than 0 or not

* added doctest and updates the else after checking if posiiton argument less than 0 or not

* fixed the contributing.md mistake

* added doctest for out of bounds position value, both negative and positive