Added demo link for Mediawiki.

README.md

@@ -1458,7 +1458,7 @@ See also [Documentation Generators](#documentation-generators), [Wikimatrix](htt
 - [Gitit](https://github.com/jgm/gitit) - Wiki program that stores pages and uploaded files in a git repository, which can then be modified using the VCS command line tools or the wiki's web interface. `GPL-2.0` `Haskell`
 - [Gollum](https://github.com/gollum/gollum) - Simple, Git-powered wiki with a sweet API and local frontend. `MIT` `Ruby`
 - [jingo](https://github.com/claudioc/jingo) - Git based wiki engine written for node.js, with a decent design, a search capability and good typography. ([Demo](http://jingo.cica.li:6067/wiki/home)) `MIT` `Nodejs`
-- [Mediawiki](https://www.mediawiki.org/wiki/MediaWiki) - MediaWiki is a free and open-source wiki software package written in PHP. It serves as the platform for Wikipedia and the other Wikimedia projects, used by hundreds of millions of people each month. ([Source Code](https://phabricator.wikimedia.org/diffusion/MW/)) `GPL-2.0` `PHP`
+- [Mediawiki](https://www.mediawiki.org/wiki/MediaWiki) - MediaWiki is a free and open-source wiki software package written in PHP. It serves as the platform for Wikipedia and the other Wikimedia projects, used by hundreds of millions of people each month. ([Demo](https://en.wikipedia.org/wiki/Main_Page), ([Source Code](https://phabricator.wikimedia.org/diffusion/MW/)) `GPL-2.0` `PHP`
 - [MoinMoin](https://moinmo.in/) - Advanced, easy to use and extensible WikiEngine with a large community of users. ([Source Code](http://hg.moinmo.in/moin)) `GPL-2.0` `Python`
 - [Olelo](https://github.com/minad/olelo) - Olelo is a wiki that stores pages in a Git repository, supports many markup styles and has an extensible, hackable architecture. ([Demo](http://gitwiki.org/)) `MIT` `Ruby`
 - [Outline](https://www.getoutline.com/) `⚠` - An open, extensible, wiki for your team built using React and Node.js. ([Source Code](https://github.com/outline/outline)) `BSD-3-Clause` `Nodejs`