Merge pull request #26 from xixu-me/dependabot/pip/sphinx-rtd-theme-gte-3.1.0

Update sphinx-rtd-theme requirement from >=2.0.0 to >=3.1.0

docs/requirements.txt

@@ -1,6 +1,6 @@
 # Documentation requirements for Sphinx
 sphinx>=7.1.0
-sphinx-rtd-theme>=2.0.0
+sphinx-rtd-theme>=3.1.0
 myst-parser>=3.0.0
 sphinxcontrib-napoleon>=0.7
 linkify-it-py>=2.1.0