docs: Add readthedocs.yml to build docs

Author: tembleking

.readthedocs.yml

@@ -0,0 +1,13 @@
+
+version: 2
+
+sphinx:
+  configuration: docs/conf.py
+
+python:
+  version: 3.6
+  install:
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs