Bump version of webpack hack

webpack.config.esm.ts

@@ -56,7 +56,7 @@ const hasGit = fs.existsSync(path.resolve(__dirname, '.git'));
 // Hack alert: due to a variety of issues, sometimes we need to change
 // the name here. Mostly it's things like webpack changes that affect
 // how minification is done, even though that's supposed not to matter.
-const webpackJsHack = '.v25.';
+const webpackJsHack = '.v26.';
 const plugins: Webpack.WebpackPluginInstance[] = [
     new MonacoEditorWebpackPlugin({
         languages: [