Please, add the subsequence predicate function

The [subsequence](https://en.wikipedia.org/wiki/Subsequence) predicate function use example is the textual fuzzy search.

In the most basic implementation, fuzzy search == subsequence search, as a defining feature of it. Examples of subsequence search being the main feature of fuzzy search are several I know of, the closest to me would be Emacs `helm` `fuzzy-find`, which for file name search does plain subsequence search to be fast.

The `isSubsequenceOf` exists in [`Data.List`](https://hackage.haskell.org/package/base-4.15.0.0/docs/src/Data-List.html#isSubsequenceOf).

To implement textual fuzzy search, the Text-specialized function needs to exist, so while being at it, would try to submit it.