bug(dependency missing): Added pyyaml

[caviri]

  File "/usr/local/lib/python3.9/site-packages/gimie/project.py", line 27, in <module>
    from gimie.parsers import parse_files
  File "/usr/local/lib/python3.9/site-packages/gimie/parsers/__init__.py", line 25, in <module>
    from gimie.parsers.cff import CffParser
  File "/usr/local/lib/python3.9/site-packages/gimie/parsers/cff.py", line 20, in <module>
    import yaml
ModuleNotFoundError: No module named 'yaml'

Problem importing gimie as a package. Added pyyaml as dependency.

I didn't rebuilt the lock file with poetry.