add missing [docs] dependencies, pin sphinx to a new version, point readthedocs to a .[docs] installation

.readthedocs.yaml

@@ -15,7 +15,14 @@ build:
 sphinx:
   configuration: docs/conf.py
 
-# Explicitly set the version of Python and its requirements
 python:
   install:
-    - requirements: docs/requirements.txt
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs
+
+# Explicitly set the version of Python and its requirements
+# python:
+#   install:
+#     - requirements: docs/requirements.txt

docs/requirements.txt

@@ -1,3 +1,4 @@
+# TODO: delete this file as it is no longer used to build the docs
 # Defining the exact version will make sure things don't break
 sphinx==5.3.0
 sphinx_rtd_theme>=0.5.1

pyproject.toml

@@ -75,10 +75,12 @@ benchmark = [
 
 # dependencies to build the docs
 docs = [
-    "sphinx",
+    "sphinx==8.1.3", # pin for stability of docs builds
     "sphinx-design",
     "sphinx-copybutton",
     "sphinx-hoverxref",
+    "sphinx-rtd-theme",
+    "sphinx_autodoc_typehints",
 ]
 
 # all dependencies