📚 DOCS: Add PDF format to the Read The Docs config (#116)

* Add PDF format to Read The Docs config

That way users can preview tabbed PDF output in the official docs.

* Fix trailing whitespace error

That is what I get for using the GitHub interface to make changes

Co-authored-by: Jared Dillard <jared.dillard@joby.aero>

Author: jdillard

.readthedocs.yml

@@ -9,3 +9,6 @@ python:
 sphinx:
   builder: html
   fail_on_warning: true
+
+formats:
+  - pdf