extending and fixing data type inside variable of CSAFParser class

[S-Panta]

Hi, I am trying to use your library to parse CSAF advisories. I see that generator.py and analyzer.py are robustly done and useful in the task.
However, CSAFParser seems to miss many elements in the generator and analyzer. Do you know if we are not supposed to use this standalone class?

Till today, I have found many missing elements in the parser and if possible I would like to contribute to the library.

• If possible, CSAFParser class could be made flexible so that it would allow for JSON object of csaf adversaries data. For example, fetching the URL of the advisory returns JSON data. If this is done, parsing all elements would be easier.
• data type in some keys in the document, product, and vulnerability are not flexible. Some value could store arrays while the code only store a single value.