Bug 27643: Add CodeMirror custom syntax highlighting for SQL runtime parameters

Bug 27643: Add CodeMirror custom syntax highlighting for SQL runtime parameters

This patch adds some additional configuration to CodeMirror so that
runtime parameters have a distinct color in the CodeMirror SQL editor.

To test, apply the patch and create or edit an SQL report which contains
one or more runtime parameters, e.g. <<branches>>, <<categorycode>>,
etc.

Confirm that when editing the SQL, these parameters should appear as
green text. Save your report and view it. The syntax highlighting should
be updated in this view too.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>