Syntax highlighting in XML editor

This would be really helpfull and would bring Inkscape a step further to
be a great SVG editing tool.

Originator: NO

[ Following comments copied from a duplicate report
https://sourceforge.net/support/tracker.php?aid=1658513 ]

using gtksourceview rather than gtktextview should be enough to add this
but developers might be reluctant to add another dependancy (gedit uses
gtksourceview so it is very widely available)
If you are a developer who could provide patches they would be very
welcome.

I would strongly favour seperating out the XML editor as much as possible
and allowing a View/Edit source function that could open the current
editor or other editors which have more or different features, including
text editors, and 3rd party XML editors. that would open up many
possibilities and also reduce pressure on Inkscape developers to put more
and more work into the XML editor which reinvents so many things.