This adds an app indicator to the system tray. For now, on close the app will minimize to the indicator rather than shutting down. The app indicator handles quitting. If you want to change this to a setting let me know.
There were a few issues with libappindicator, so for now it relies on my forks. I will be submitting PRs to the appropriate repositories and changing it once accepted.
There are a few things that feel kind of hacky due to my lack of knowledge on Rust's ownership system. Let me know if anything stands out to you.