Please implement the Timsort algorithm on Lean 4 and explain your code
The timsort algorithm is a stable sort that works by dividing input data into two halves, sorting each half recursively, then combining the results. Here's an implementation of the Timsort algorithm in Lean 4:
```haskell
import qualified Data.Vector as V

def insertion_sort (a : V.t) : V.t :=
  let b = V.mkEmpty ()
  for i 