Try to fix the RTD builds

.readthedocs.yaml

@@ -0,0 +1,30 @@
+# Read the Docs configuration file for Sphinx projects
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the OS, Python version and other tools you might need
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.11"
+
+# Build documentation in the "docs/" directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
+# Optionally build your docs in additional formats such as PDF and ePub
+# formats:
+#    - pdf
+#    - epub
+
+# Optional but recommended, declare the Python requirements required
+# to build your documentation
+# See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
+python:
+  install:
+    - method: pip
+      path: .
+      extra_requirements:
+        - documentation

pyproject.toml

@@ -39,7 +39,7 @@ Changelog = "https://github.com/MSeifert04/iteration_utilities/blob/master/docs/
 
 [project.optional-dependencies]
 test = ["pytest"]
-documentation = ["sphinx", "numpydoc",]
+documentation = ["sphinx>=2.2", "numpydoc"]
 
 [tool.pytest.ini_options]
 addopts = "--doctest-glob='docs/*.rst' --ignore='setup.py'"