You are given a list of non-overlapping intervals already sorted by start, where intervals[i] = [startᵢ, endᵢ], and a single newInterval = [start, end].
Insert newInterval into the list so the result stays sorted by start and remains non-overlapping (merge with any intervals it touches or overlaps). Return the updated list.
Two intervals overlap when they share at least one point, so [1,3] and [3,5] merge into [1,5].
[[1,3],[6,9]], [2,5][[1,2],[3,5],[6,7],[8,10],[12,16]], [4,8][], [5,7][[1,5]], [2,3][[1,5]], [6,8][[3,5],[8,10]], [1,2][[1,2],[5,6]], [3,4]