feat:Anonymization skill

[OrianeLanfranchi]

Addition: new indexer skill

Anonymization skill :

• optional skill
• to be used after FileReader skill and before text splitting skills
• sample for the config file :

  - skill: &Anonymizer
      type: anonymizer
      name : anonymizer
      params:
        use_placeholders: False

• need for pip to use the library this skill depends on. pip module is not automatically included in the venv created by uv. Need to run the following command : uv venv --seed