Add a config file

[leo-desbureaux-tellae]

A config file already exists in Starling, but we should move most of the global variables used in Starling in the config (like the data folder)

A default config containing default value for each attributes should be stored in the package.

Some of the config values are related to the actual simulation (walking speed, distance factor?), while others are related to the environment and the inputs/outputs. Should we separate these two types of configs ?

Maybe use a class like this:

class StarlingConfig:
    def __init__(self, config_dict):
        self.provided_config = config_dict
        
        final_config = copy.deepcopy(DEFAULT_CONFIG)
        final_config.update(config_dict)
        self._config = final_config
        
    @property
    def config(self):
        return self._config
    
    def __getitem__(self, item):
        return self._config[item]