Fixed broken documentation build

Author: agateblue

.readthedocs.yaml

@@ -0,0 +1,18 @@
+# .readthedocs.yaml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+build:
+  os: ubuntu-20.04
+  tools:
+    python: "3.9"
+
+sphinx:
+  configuration: docs/conf.py
+
+python:
+  install:
+    - requirements: requirements-docs.txt