Add "give me a coffee" donation link

[LeoColman]

Hi!

This app was always helpful. I'd like to donate you a coffee or two!

[thetwom]

Thanks for the kind words. Glad that the app is helpful for you. Fortunately I can do the development as a hobby project, so no need for donations.

[vocna]

@thetwom: It's a lot of work though and too I would be glad to support you.❤️ I think README is a good place adding link to donating, but I opposite adding such link to the app.