Custom linked list module.

append(value) adds a new node containing value to the end of the list.

prepend(value) adds a new node containing value to the start of the list.

size returns the total number of nodes in the list.

headNode returns the first node in the list.

tailNode returns the last node in the list.

getNodeAt(index) returns the node at the given index.

pop removes the last element from the list.

contains(value) returns true if the passed in value is in the list and otherwise returns false.

indexOf(value) returns the index of the node containing value, or null if not found.

toString represents your LinkedList objects as strings, so you can print them out and preview them in the console. The format should be: ( value ) -> ( value ) -> ( value ) -> null

insertAt(value, index) inserts a new node with the provided value at the given index.

removeAt(index) removes the node at the given index.

clear() clears the linked list.