migrate katex ( js portion ) to js bundle

assets/scripts/features/index.js

@@ -17,3 +17,7 @@ if (process.env.FEATURE_FLOWCHART) {
 if (process.env.FEATURE_SYNTAXHIGHLIGHT) {
   import('./syntaxhighlight');
 }
+
+if (process.env.FEATURE_MATH) {
+  import('./math');
+}

assets/scripts/features/math/index.js

@@ -0,0 +1,3 @@
+if (process.env.FEATURE_MATH_KATEX) {
+  import('./katex');
+}

assets/scripts/features/math/katex.js

@@ -0,0 +1,21 @@
+import renderMathInElement from 'katex/contrib/auto-render';
+import * as params from '@params';
+
+const defaultOptions = {
+  delimiters: [
+    {left: "$$", right: "$$", display: true},
+    {left: "\\[", right: "\\]", display: true},
+    {left: "$", right: "$", display: false},
+    {left: "\\(", right: "\\)", display: false}
+  ]
+}
+
+window.addEventListener('DOMContentLoaded', () => {
+  renderMathInElement(
+    document.body,
+    {
+      ...defaultOptions,
+      ...(params.math?.katex || {}),
+    }
+  );
+});