Feature request: date normalizer & format parser

[percevalw]

Feature type

Once a date has been extracted by the ML NER module (e.g., eds.ner_crf), it still needs to be normalized, and its format extracted to be able to shift it before replacing it in the pseudonymized report.

The normalizer should assign a date attribute (edsnlp's AbsoluteDate) and a date format (either strftime's %d %m %Y or java's dd-mm-yyyy, compatible with pendulum). The question is not format syntax is not trivial, since C standard date format, since strftime does not support case modifiers (a full letter month will always be replaced in titlecase), nor full letter numbers.

[percevalw]

Completed in #11