Added cluster labeling functionalities

[MattVsTheWorld]

Adding cluster labeling functionalities.

Given a FuzzySystem with a defined universe of discourse for its linguistic variables, you can utilize the following function to perform cluster labeling:

approximate_fs_labels(fs: FuzzySystem, output_path: str, generate_report: bool)

Parameters:

• fs: An instance of simpful FuzzySystem;
• output_path: A string specifying the path where the output will be saved;
• generate_report: A boolean indicating whether to generate a pdf report with plots and rules.

Example can be found in simpful/cluster_labeling/tests/automatic_report_test.py.