No insert-by-index operation for OSet

[arrowd]

The library does not provide a way to insert an element near the given index. I ended up writing it myself via fold:

insertOSet :: WhereTo -> OSet a -> a -> OSet a -> OSet a
insertOSet appendOrPrepend elemsToInsert targetElem set = unbiased $ foldMap' g set
  where
    g e = (Bias :: a -> Bias L a) $
      if e == targetElem
        then if appendOrPrepend == Prepend
          then elemsToInsert |> e
          else e |< elemsToInsert
        else
          singleton e

It'd be nice to have a proper implementation of this function in the library.

[arrowd]

Err, my code actually inserts near given element, not the given index.