Describe Bahtinov focus in KStars Documentation/Handbook
In June 2020 a message was posted on the Kstars-devel mailing list, requesting more information about the Bahtinov focus assistant. "I would like to know more about the Detection drop down menu items in *Ekos -> Focuser -> Process *panel., especially *Bahtinov. *But I wasn't able to find an explanation of them in the KStars Documentation/Handbook."
This issue is to update the docbook with this information.