readthedocs: add configuration file

.gitignore

@@ -67,3 +67,4 @@ test.sh
 !/suricata-update/Makefile.am
 /libsuricata-config
 !/libsuricata-config.in
+!/.readthedocs.yaml

.readthedocs.yaml

@@ -0,0 +1,9 @@
+# Required by Read The Docs
+version: 2
+
+python:
+  version: "3.8"
+
+  # Use an empty install section to avoid RTD from picking up a non-python
+  # requirements.txt file.
+  install: []