Restore progress as it is used by autograding.

Author: uhafner

etc/bootstrap-custom-build.scss

@@ -55,6 +55,7 @@ th {
 @import "../node_modules/bootstrap/scss/pagination";
 @import "../node_modules/bootstrap/scss/badge";
 @import "../node_modules/bootstrap/scss/alert";
+@import "../node_modules/bootstrap/scss/progress";
 @import "../node_modules/bootstrap/scss/list-group";
 @import "../node_modules/bootstrap/scss/close";
 @import "../node_modules/bootstrap/scss/toasts";