Release 0.8.0

[ConstantineLignos]

Major changes:

• Drop support for Python 3.9 and add support for Python 3.14
• Changes default output delimiter for CoNLL files to tab
• Add check for empty tokens during validation
• Enable setting the field index of the token and label as command-line arguments (--token-index and --label-index)
• Increase test coverage to 100%
• Move all project setup to pyproject.toml and remove setup.py and requirements.txt
• Add release script