How do this website do it? (Wikiwand.com loads Wikiepdia and apply Style to it)

I need to load Wikipedia from my site and apply some "readability" Style to it.

For example:

This is a Wikipedia regular page: https://en.wikipedia.org/wiki/Glass

Then, if one changes the domain to wikiwand's: https://www.wikiwand.com/en/Glass

It opens the same page more a lot more readable and beautiful.

Screenshots:

Glass article on Wikipedia https://prnt.sc/oy9ati

Glass article viewed through Wikiwand website. https://prnt.sc/oy9chd