While doing a simple [Exercism problem](https://exercism.org/tracks/nim/exercises/sublist), I needed to check whether one sequence was a subsequence of another. Having done similar things in Haskell, I was hoping there would be similar functions in `sequtils` to Haskell's `isPrefixOf` / `isInfixOf` but couldn't find anything. There's a `contains` function but of the form `a: Seq[T], b: T`, so that'll only look for a single element. But `strutils` has a different `contains(a, b: string)` \-- that would seem like what I was missing for sequence types.
Is there something like that in the stdlib that's not specialised to strings? I ended up doing it the naieve way by repeatedly comparing one sequence against sliding slices of the other sequence, which isn't super efficient compared to something like [two-way string matching](https://en.wikipedia.org/wiki/Two-way_string-matching_algorithm) or <https://en.wikipedia.org/wiki/Boyer%E2%80%93Moore_string-search_algorithm>.
