Major updates to the library's core.
- Support for different layouts and multiple viewports.
- Support for settings (saved to disk as a JSON file).
- Better default values for less user configuration.
- Removal of the global event messaging system in favor of a top-down notification approach.
- Overhaul of key bindings and how they are mapped onto commands.
- Organization of code into various subpackages.
- Continued correction of `pylint` and `pydocstyle` errors.
- Use of `pytest` for testing and continued improvement of test coverage.