Web apps don't autostart

1. Go to `chrome://app-settings`
2. Enable "Start app when you sign in" for a web app
3. It doesn't autostart

**Note:** this occurs even when explicitly giving the Flatpak permissions for it. I didn't investigate but I guess it might be an issue with Flextop?

Original report: https://github.com/ungoogled-software/ungoogled-chromium-flatpak/issues/22