Currently I am working on a part of a wikimirror project that involves doing a search in wikipedia and retrieving snippet of text with searched terms being highlighted.

I would like to improve what I am doing at the moment by highlighting also different forms of a given word.
For example if user types in: 'playing' I would also highlight play, plays, played and so on.
In wikipedia this already works like this:
https://en.wikipedia.org/w/index.php?title=Special%3ASearch&profile=default&search=playing+outside&fulltext=Search
I would like to ask what technics (plugins, libraries, extensions) wikipedia uses to do this type of highlighting.
I would appreciate any answer.