Set new required build fields in the ReadTheDocs config file (#1803)

* Set the OS in the ReadTheDocs build process

* Add required tools.python to ReadTheDocs config file

* Change Python version from number to a string

.readthedocs.yaml

@@ -5,6 +5,13 @@
 # Required
 version: 2
 
+# Set the OS
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3"
+
+
 # Build documentation in the docs/ directory
 mkdocs:
   configuration: mkdocs.yml