chore: :recycle: Update RIXSConverter class documentation and argument descriptions
Update the documentation and argument descriptions in the RIXSConverter class to provide clearer explanations and improve readability. This commit also renames some argument labels for consistency and adds default values for certain arguments. The changes aim to enhance the understanding and usability of the RIXSConverter class for converting raw pickle data into JSON, TOML, or numpy formats for RIXS visualization.
