Shiki perf (#197)

* shiki cache + no explanation

* Remove dev optimization

With includeExplanation fix gain become negligible

* Add  doc

* fix codestyle

src/docs/lib/shiki.ts

@@ -11,35 +11,44 @@ const theme: Theme = "github-dark";
 const defaultlangs: Lang[] = ["html", "tsx"];
 const bg: React.CSSProperties["backgroundColor"] = "#011627";
 
+const highlighterCache = new Map<string, Promise<Highlighter>>();
+
+/**
+ * Get a shiki highlighter instance.
+ * Cached by theme and languages.
+ */
 export async function getHighlighter({
   langs = defaultlangs,
 }: {
   langs?: Lang[];
-} = {}) {
-  /** Preload NO languages in development */
-  const isDevelopment = process.env.NODE_ENV === "development";
+} = {}): Promise<Highlighter> {
+  const key = [theme, ...langs].join("-");
+
+  const highlighter = highlighterCache.get(key);
+  if (highlighter) return await highlighter;
 
   /* ✅ Create a highlighter instance with a theme */
-  return await getHighlighterFromShiki({
+  const highlighterPromise = getHighlighterFromShiki({
     theme,
-    langs: isDevelopment ? [] : langs,
+    langs,
   });
+  highlighterCache.set(key, highlighterPromise);
+  return await highlighterPromise;
 }
 
+/**
+ * Highlight code string with provided shiki highlighter.
+ * includeExplanation turned off to increase performance.
+ */
 export async function highlight(
   highlighter: Highlighter,
   code: string,
   lang: Lang = "tsx"
 ) {
-  /** Request NO languages in development */
-  const isDevelopment = process.env.NODE_ENV === "development";
-
   /* ✅ Highlight your code using the right syntax */
-  const tokens = highlighter.codeToThemedTokens(
-    code,
-    isDevelopment ? "" : lang,
-    theme
-  );
+  const tokens = highlighter.codeToThemedTokens(code, lang, theme, {
+    includeExplanation: false,
+  });
   /* ⚠️ Optional: Custom rendering of code blocks */
   return renderToHtml(tokens, {
     bg,