Think Greasemonkey for more advanced users.
It works by matching every page domain against script file names available in the scripts folder. For instance, if one navigates to
www.google.com, Witchcraft will try to load and run
For more information on how to install and use it, head to Witchcraft's home page.
Witchcraft is my rendition of defunkt's original extension, dotjs. Although I never got to actually use dotjs (it only worked for MacOS and the installation process was not easy), I really wanted something like that. Thanks, defunkt, for having such a cool idea.
Thanks arimus for the idea of using Web Server for Chrome.
The little witch and the witch hat icons were provided by Freepik.