chore: fix demos on windows

Author: Matt Lewis

webpack.config.ts

@@ -36,7 +36,7 @@ export default {
       test: /\.(ttf|eot|svg)(\?v=[0-9]\.[0-9]\.[0-9])?$/,
       loader: 'file-loader'
     }, {
-      test: /demos\/.+\.(css|html)$/,
+      test: /demos[\/\\].+\.(css|html)$/,
       loader: 'raw-loader'
     }, {
       test: /\.ejs$/,