Problem - Insert Interval

Given a sorted list of non-overlapping intervals and a new interval, insert the new interval and merge if necessary. Return the result still sorted and non-overlapping.

Example: intervals $= [[1,3], [6,9]]$, new $= [2,5]$ returns $[[1,5], [6,9]]$. This builds on merge intervals but requires handling the insertion point. Constraints: up to $10^4$ intervals.