added arr. methods to Javascript

[FarhadIbrahimov]

// Instance: iteration methods
arr@@iterator // Returns a new Array Iterator object that contains the values for each index in the array. (Same as arr.values())

// Instance: accessor methods
arr.flat(depth) // Creates a new array with all sub-array elements concatenated up to the specified depth.

// Instance: mutator methods
arr.populate(length, value) // Fills the array with the specified value to a given length.
arr.shuffle() // Randomly shuffles the elements of the array in place.

// Instance: utility methods
arr.isEmpty() // Checks if the array is empty and returns a boolean value.
arr.sample() // Returns a random element from the array without modifying the array.