Initial release

The first release of curies contains the Converter with methods for simple prefix maps, i.e., dictionaries whose keys are arbitrary prefixes like chebi and whose values are there corresponding URI prefixes like http://purl.obolibrary.org/obo/CHEBI_. Ideally, the prefixes correspond to a high-quality registry such as the Bioregistry. Future releases will have utilities for getting prefix maps from the Bioregistry and other registries.