To generate dash documentation you need dashing utility (https://github.com/technosophos/dashing) in your path.

Run this command to generate docset:

dashing build

To use docset in Zeal copy it to your docset directory (in linux - ~/.local/share/Zeal/Zeal/docsets/)

More information available at https://zealdocs.org/.