The kdmod module was broken since we renamed packages/ to src/. Also,
the update to mod loading for some unknown reason now requires each call
to require to end with `.js`. As far as I know, this was working
previously.
Allows modules to register a listener to the 'install' event without
creating a Module class. This changes how external modules are
installed.
External modules are now referred to as "extensions"; this commit does
not update the term but does use 'extension' as the name of the global.
