How to add another script extension for syntax highlighting in gedit:

First step is to go to the following directory:
gz@osx~# cd /Applications/gedit.app/Contents/Resources/share/gtksourceview-2.0/language-specs

There you will find a bunch of *.lang files.
My goal was to add *.ksh extension with the same highlighting like *.sh so I edited sh.lang as follows:
Open the file and search for:
<property name="globs">*.sh</property>.
Then replace it with:
<property name="globs">*.sh;*.ksh</property>.