Adding `intersperse` to the API

I would like to suggest the addition of `intersperse :: a -> Vector a -> Vector a` to the API.

I have a prototype that I reuse in my projects, that reads:

```haskell
intercalateVec :: Text -> Vector Text -> Vector Text
intercalateVec sep vector =
if V.null vector
then vector
else V.tail $ V.concatMap (\word -> V.fromList [sep, word]) vector
```

But I would be interested to know if a better implementation is possible.