We heard this feedback infact and we wrote the entire plugin system for webpack 4! (https://github.com/webpack/tapable). Take a look at the only PR open which is us working to provide the best Type system possible for our new API (which was infact designed to support it).

Even better is that you can find all the "hooks" on an instance by doing `compiler.hooks` so now you get a far better authoring experience :-D