Add newly-required ReadTheDocs configuration file

.readthedocs.yaml

@@ -0,0 +1,14 @@
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
+# Version of Python and requirements required to build the docs
+python:
+  install:
+    - requirements: docs/requirements.txt