docs: Add readthedocs config

Signed-off-by: Robert Winkler <rwinkler@antmicro.com>

.readthedocs.yml

@@ -0,0 +1,14 @@
+# .readthedocs.yml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+version: 2
+
+sphinx:
+  configuration: docs/conf.py
+  fail_on_warning: true
+
+python:
+  version: 3.7
+  install:
+    - requirements: docs/requirements.txt