Add Donate button in app

[Volodymyr-13]

Describe

I think it's good idea to add a nice green button into ToolBar.

And, the last menu could be - Hide, which will hide this button until next update of the app.

[kode54]

I'll think about it. I also have to implement it completely differently in the App Store version, because it will need to be through In App Purchases instead of any of those external sites.