doc: Use readthedocs config file (#2957)

This is the recommended way to configure the project instead of using
the website.

It should also help fix readthedocs/readthedocs.org#10290

.readthedocs.yaml

@@ -0,0 +1,22 @@
+---
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the version of Python and other tools you might need
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3"
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: doc/conf.py
+  fail_on_warning: true
+
+# If using Sphinx, optionally build your docs in additional formats such as PDF
+# formats:
+#    - pdf