Please consider adding an index

[markmcn]

Hey,
Working from version 2.0 of the book,
It's great but it's difficult to pickup and use a a reference text for quick reminders on topics as there is no index at the back where I can look up where topics are covered, Eg what page can I skip to to get a reminder about registering out put or how can I use facts.
Don't get me wrong the chapter list at the front is great but it's not the same as an index,
Please consider adding/publishing an index. As someone who doesn't use ansible everyday and needs to pick this up for quick refreshers when I'm writing a playbook that would be helpful

[geerlingguy]

Thanks! Please see #541 and follow that for progress :)