Lightbulb-ext-hecate

Breaking
- Modifiers `on_method_enter` and `on_method_exit` are now `on_command_enter` and `on_command_exit`, respectively.

New stuff
- Template generation with `python -m lightbulb.ext.hecate --template PATH`.
- Modifiers placed on `__modify__.py`, adjacent to the module, are now accepted, given they have the right name.
- The whole README and docstrings

- Implement `hecate.Plugin` subclass.
- Implement command side classes `Params`, `Option` and `Properties` to declare necessary command attributes.
- Implement custom errors and logging.
- Implement `on_command_error`, `on_event_error`, `on_method_enter` and `on_method_exit` as arguments for the `Plugin` class to add functionality to commands and events in files in the extension scope.