Please, add the subsequence predicate function #368

The 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.

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