Readthedocs: add explicit requirement sphinx_rtd_theme

Closes #269.

.readthedocs.yaml

@@ -24,9 +24,8 @@ sphinx:
 #    - pdf
 #    - epub
 
-# Optional but recommended, declare the Python requirements required
-# to build your documentation
+# Declare the Python requirements required to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
-# python:
-#    install:
-#    - requirements: doc/requirements.txt
+python:
+   install:
+   - requirements: doc/requirements.txt

doc/conf.py

@@ -46,10 +46,10 @@
 #
 html_theme = 'sphinx_rtd_theme'
 
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+# # Add any paths that contain custom static files (such as style sheets) here,
+# # relative to this directory. They are copied after the builtin static files,
+# # so a file named "default.css" will overwrite the builtin "default.css".
+# html_static_path = ['_static']
 
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'

doc/requirements.txt

@@ -0,0 +1,2 @@
+Sphinx           >= 7.2.5
+sphinx_rtd_theme >= 1.3.0