gnucash-docs maint: Add an install target for html.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash-docs/commit/fd06fa21 (commit)
	from  https://github.com/Gnucash/gnucash-docs/commit/e0268667 (commit)



commit fd06fa21df847b4b70e797cb3221c4e2dee09808
Author: John Ralls <jralls at ceridwen.us>
Date:   Tue Aug 18 16:53:47 2020 -0700

    Add an install target for html.
    
    Needed for macOS bundling.



Summary of changes:
 cmake/AddHtmlTarget.cmake | 3 +++
 1 file changed, 3 insertions(+)