chore(deps): update to webpack 5 (#2664)

Co-authored-by: Kevin Barabash <kevinb@khanacademy.org>

webpack.dev.js

@@ -12,17 +12,19 @@ katexConfig.entry.main = './static/main.js';
 // only the `devServer` options for the first configuration will be taken
 // into account and used for all the configurations in the array.
 katexConfig.devServer = {
-    contentBase: [path.join(__dirname, 'static'), __dirname],
+    static: [
+        path.join(__dirname, 'static'),
+        {
+            directory: __dirname,
+            watch: false,
+        },
+    ],
     // Allow server to be accessed from anywhere, which is useful for
     // testing.  This potentially reveals the source code to the world,
     // but this should not be a concern for testing open-source software.
-    disableHostCheck: true,
+    firewall: false,
     host: '0.0.0.0',
     port: PORT,
-    sockPort: 'location',
-    stats: {
-        colors: true,
-    },
 };
 
 module.exports = ([