Adds Preferences Window for Managing Shortcuts

[ravero]

With this PR I've tried to manage the only thing that bothered me in the app, the Global Keyboard shortcuts (more specifically the Play/Pause using the Cmd+Shift+Spacebar) that was conflicting with other program that I was using this shortcut to (1Password 8).

In order to collaborate and not break existing functionality that others may be used and interested, I've implemented a preferences window that allow enabling/disabling those shortcuts. This should at least avoid the hotkeys conflict. A further improvement on this implementation would be to allow custom Shortcuts altogether, but I've found that it would require more effort than I currently would put on this.

I hope this addition helps to enhance the value of the app which for me, as a YouTube Music user, is a must on macOS.