No effect of adding CSS

Hello! Many thanks for creating this template.

I've used the `npx imba create my-app` to bootstrap an electron app. I noticed issue #1 and besides, I also see that adding CSS has no effect.

You can use this reproduction repo: https://github.com/nayaabkhan/imba-electron-css

I've added a global and local CSS declaration on these lines:
- https://github.com/nayaabkhan/imba-electron-css/blob/master/app/renderer.imba#L8
- https://github.com/nayaabkhan/imba-electron-css/blob/master/app/renderer.imba#L18

Start by running the reproduction repository linked in the issue and inspect the CSS declarations in app/renderer.imba at lines 8 and 18. Verify the global and local styles in the generated Electron app, then confirm that both declarations visibly affect the rendered output.

Written by the indexing model from the issue text.