docs: Install sphinx-rtx-theme

.readthedocs.yaml

@@ -3,5 +3,8 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.12"
+python:
+  install:
+    - requirements: docs/requirements.txt
 sphinx:
   configuration: docs/conf.py

docs/conf.py

@@ -25,7 +25,7 @@ import sys, os
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = []
+extensions = ['sphinx_rtd_theme']
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']

docs/requirements.txt

@@ -0,0 +1 @@
+sphinx-rtd-theme==1.3.0