[Feature Request] Do not spawn a new instance when running it again

[barraIhsan]

What I meant by this is that when trackma (gui) launched the second time even though it's already running, just replace the old one with the new one.

This happened to me a lot when Close to tray turned on, not realizing it's already launched, I launch it again using a menu launcher and it end up having 2 instance of trackma running.

My suggestion is that it should work just like qBittorrent and Discord, if we try to launch it again, it will just raise and show that window (if it's configured to close to tray) instead of spawning a new one

Also related: #676 if it does running as daemon, every gui instance will just connect to that daemon

[z411]

This was desired behavior as some people use multiple instances to update several websites as once. That said I feel using a single instance should be the default behavior, and allowing multiple instances could be enabled through a command-line flag or config option.