Features extraction

What the MR does

• added module to extract important features from the text (doc and tests)
• notebook checking generation & analysing texts (originals and generated).

Checklist

• Linting and typing are OK,
• Licenses are OK (licensecheck + integration with reuse with the proper licenses),
• You have tested this MR locally,
• You have considered performance issues,
• You have considered availability and reliability risks,
• You have updated documentation if necessary.

Linked to issue #19