fix: Missing dependencies

Addition of Sphinx dependencies in requirements.txt

Author: lahovniktadej

docs/requirements.txt

@@ -4,4 +4,7 @@ pandas>=2.1.1,<3.0.0
 nltk>=3.8.1,<4.0.0
 plotly>=5.22.0,<6.0.0
 scikit-learn>=1.5.1,<2.0.0
+sphinx-rtd-theme>=1.0.0,<2.0.0
+sphinxcontrib-bibtex>=2.4.1,<3.0.0
+sphinx>=7.2.6,<8.0.0
 tomli>=2.0.1,<3.0.0; python_version < "3.11"