feat(build): support code highlight in uppercase (#1082)

fixes #772

Co-authored-by: Divyansh Singh <40380293+brc-dd@users.noreply.github.com>

src/node/markdown/plugins/highlight.ts

@@ -14,7 +14,7 @@ export async function highlight(theme: ThemeOptions = 'material-palenight') {
 
   return (str: string, lang: string) => {
     const vPre = vueRE.test(lang) ? '' : 'v-pre'
-    lang = lang.replace(vueRE, '')
+    lang = lang.replace(vueRE, '').toLowerCase()
 
     if (hasSingleTheme) {
       return highlighter