[fix] build workflows of the themes

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

utils/lib_sxng_test.sh

@@ -89,7 +89,6 @@ test.robot() {
     dump_return $?
 }
 
-
 test.rst() {
     build_msg TEST "[reST markup] ${RST_FILES[*]}"
 
@@ -98,6 +97,12 @@ test.rst() {
     done
 }
 
+test.themes() {
+    build_msg TEST 'SearXNG themes'
+    themes.test
+    dump_return $?
+}
+
 test.pybabel() {
     TEST_BABEL_FOLDER="build/test/pybabel"
     build_msg TEST "[extract messages] pybabel"