[Feature] Develop a userChrome CSS Theme for FireFoxPWA

[quebexer]

FirefoxPWA let's you install PWAs like if they were native apps. However, when you install them, they keep the original Firefox theme. I tried installing your Gnome Theme but it looks odd. See the picture below for comparison.

[LSeelig]

I use a custom default profile so apps automatically use the native titlebar (the extensions button and permissions can still be accessed with ctrl-tab) but supporting firefoxpwas would mean right click menus, other ui elements, and maybe the more useful custom titlebars would integrate better.

[rafaelmardojai]

I use Fedora Silverblue and Flatpaked Firefox, and installing this extension to try to support it seems impossible. PRs will be very welcome if anyone actually using the extension can work on this.

[LSeelig]

I don't know if/how it can be done with a flatpak since I use the rpm Firefox on Fedora Workstation.