Sender must check window before closing

[May-Lee]

If I have a lot of tabs open, and have sent a number of files using Winden, then if I want to close any tabs, I need to check my windows to see if they have sent.

Some suggestions:

• something like a favicon change/notification that would let me know it's okay to close my tab without having to check back at it
• Have some sound and/or desktop notification
• Have the sending in a pop up window that closes automatically when done

[donpui]

I think reusing favicon icon as status would be nice improvement. Example here: https://www.npmjs.com/package/favicon-notification

Also we could identify several states: receiver accepted code, receiver rejected code, receiver is downloading, download completed.

[donpui]

@May-Lee there was some improvement with release https://github.com/LeastAuthority/winden/releases/tag/0.5.3-beta, which can help this issue. Now users gets warning if they try close browser while code is not accepted or transfer is going on. Please check and give feedback