Bug 30212: Make Select2 available for ILL backends

This patch makes select2 available for ILL backend developers to use on
their templates.

To test:
1. Have a configured backed and an ILL request
2. Open the inspector and load any action on the backend (intranet)
=> FAIL: no select2 asset is transfered from Koha to the browser
3. Apply this patch
4. Reload
=> SUCCESS: There's select2
5. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit c864cc73e5)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
(cherry picked from commit 710344a560)
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>

koha-tmpl/intranet-tmpl/prog/en/modules/ill/ill-requests.tt

@@ -810,6 +810,7 @@
     [% INCLUDE 'datatables.inc' %]
     [% INCLUDE 'columns_settings.inc' %]
     [% INCLUDE 'calendar.inc' %]
+    [% INCLUDE 'select2.inc' %]
     [% Asset.js("lib/jquery/plugins/jquery-ui-timepicker-addon.min.js") | $raw %]
     <script>
         var prefilters = '[% prefilters | $raw %]';