Merge Overalapping Intervals

Write a function that takes in a non-empty array of arbitrary intervals, merges any overlapping intervals, and returns the new intervals in no particular order.

Each interval interval is an array of two integers, with interval[0] as the start of the interval and interval[1] as the end of the interval.

Note that back-to-back intervals aren't considered to be overlapping. For example, [1, 5] and [6, 7] aren't overlapping; however, [1, 6] and [6, 7] are indeed overlapping.

Also note that the start of any particular interval will always be less than or equal to the end of that interval.

Example #1:

Input:

intervals = [[1, 2], [3, 5], [4, 7], [6, 8], [9, 10]]

Output:

[[1, 2], [3, 8], [9, 10]]