migrate doc links from https://github.com/pyllyukko/user.js/wiki/Extensions-&-Plugins Part of #220
migrate doc links from https://github.com/pyllyukko/user.js/wiki/Extensions-&-Plugins
Part of #220

pyllyukko/user.js,nodiscc/user.js,pyllyukko/user.js,nodiscc/user.js,Toromtomtom/user.js,Toromtomtom/user.js