bump(v0.4.0): The Alchemist

This version includes:

- easier definition of entry points (with a `entry` class to ultimately
  force it);
- a way to limit the generated entry points by providing a required
  prefix to their path;
- a way to list valid entry points without tangling any code;
- minor QOL fixes on error messages;
- updated documentation along with instructions on how to compile
  the project with Docker;