Add doc building dependencies

setup.cfg

@@ -23,7 +23,7 @@ classifiers =
     Topic :: Utilities
 
 project_urls =
-    Source Code = https://github.com/drewcassidy/yaclog
+    Source = https://github.com/drewcassidy/yaclog
     Changelog = https://github.com/drewcassidy/yaclog/blob/main/CHANGELOG.md
 
 [options]
@@ -34,6 +34,13 @@ install_requires =
 python_requires = >= 3.8
 packages = find:
 
+[options.extras_require]
+docs =
+    Sphinx >= 3.5
+    sphinx-click >= 2.7
+    sphinx-rtd-theme
+    myst-parser >= 0.14
+
 [options.entry_points]
 console_scripts =
     yaclog = yaclog.cli.__main__:cli