Update dependency sphinx-rtd-theme to v3 (release/current) (#74)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

setup.cfg

@@ -68,4 +68,4 @@ dev =
 doc =
     autoapi~=2.0.1
     sphinx-autodoc-typehints~=2.5.0
-    sphinx-rtd-theme~=2.0.0
+    sphinx-rtd-theme~=3.0.2