fix: diff2html css path

client/scss/app.scss

@@ -6,7 +6,7 @@
 
 @import '~vuescroll/dist/vuescroll.css';
 @import '~katex/dist/katex.min.css';
-@import '~diff2html/dist/diff2html.min.css';
+@import '~diff2html/bundles/css/diff2html.min.css';
 
 @import 'components/katex';
 @import 'components/v-btn';