style: change margin-buttom of code block

Author: razonyang

assets/hb/modules/bootstrap/scss/index.scss

@@ -1 +1,11 @@
 @import '../../../../mods/bootstrap/scss/index';
+
+.collapse-wrapper {
+  .highlight {
+    margin-bottom: .25rem;
+  }
+
+  pre {
+    margin-bottom: 0;
+  }
+}