Removed the remains of katex from vendor assets and load everything via webpack

app/assets/javascripts/render_math.js

 // import katex from 'katex';
+// import katexCSS from 'katex/dist/katex.css';
 import Flash from './flash';
 // Renders math using KaTeX in any element with the
@@ -28,16 +29,13 @@ function renderWithKaTeX(elements, katex) {
 export default function renderMath($els) {
   if (!$els.length) return;
-
   import(/* webpackChunkName: 'katex' */ 'katex').then((katex) => {
-    $.get(gon.katex_css_url, () => {
-      const css = $('<link>', {
-        rel: 'stylesheet',
-        type: 'text/css',
-        href: gon.katex_css_url,
-      });
-      css.appendTo('head');
+    import(/* webpackChunkName: 'katex' */ 'katex/dist/katex.css')
+    .then(() => {
       renderWithKaTeX($els, katex);
+    })
+    .catch((err) => {
+      Flash(`Can't load katex css ${err}`);
     });
   }).catch((err) => {
     Flash(`Can't load katex module: ${err}`);

config/webpack.config.js

@@ -128,6 +128,29 @@ var config = {
           name: '[name].[hash].[ext]',
         }
       },
+      {
+        test: /katex.css$/,
+        include: /node_modules\/katex\/dist/,
+        exclude: /(vendor\/assets)/,
+        use: [
+          { loader: 'style-loader' },
+          { 
+            loader: 'css-loader',
+            options: {
+              name: '[name].[hash].[ext]'
+            }
+          },
+        ],
+      },
+      {
+        test: /\.(eot|ttf|woff|woff2)$/,
+        include: /node_modules\/katex\/dist\/fonts/,
+        exclude: /(vendor\/assets)/,
+        loader: 'file-loader',
+        options: {
+          name: '[name].[hash].[ext]',
+        }
+      },
       {
         test: /monaco-editor\/\w+\/vs\/loader\.js$/,
         use: [

package.json

@@ -69,6 +69,7 @@
     "react-dev-utils": "^0.5.2",
     "select2": "3.5.2-browserify",
     "sql.js": "^0.4.0",
+    "style-loader": "^0.19.1",
     "svg4everybody": "2.1.9",
     "three": "^0.84.0",
     "three-orbit-controls": "^82.1.0",