[Feature Request]: Automatically engage picture-in-picture mode when windows is minimized or not active window

### Guidelines

- [X] I have searched the [issue tracker](https://github.com/FreeTubeApp/FreeTube/issues) for a feature request that matches the one I want to file, without success.
- [X] I have searched the [documentation](https://docs.freetubeapp.io/) for information that matches the description of the feature request I want to file, without success.

### Problem Description

I like to watch a video in fullscreen/theater mode, but I often alt+tab to another window (said window is maximized) to do something else.
I have to manually click the picture-in-picture mode button each time, if I want to keep watching the video. I am sure this can be automated like it is on Android.

### Proposed Solution

I would like an option in the settings, that makes FreeTube detect if its the active-window/visible-on-the-screen. If it is not, it engages Picture-in-Picture, and re-embeds the video when FreeTube becomes the active window again. Very much like it does on Android.

### Issue Labels

ease of use improvement

### Additional Information

I am using Windows. I only use 1 monitor on said PC.