Fix Bootstrap 5.3

Author: kishikawakatsumi

Public/scss/default.scss

@@ -1,5 +1,6 @@
 @import "bootstrap/scss/functions";
 @import "bootstrap/scss/variables";
+@import "bootstrap/scss/variables-dark";
 @import "bootstrap/scss/maps";
 @import "bootstrap/scss/mixins";
 @import "bootstrap/scss/utilities";