Full moon

[harkabeeparolus]

So I did get an idea from issue #80 (which to me appears to be some kind of spam?).

We could add https://github.com/jr-k/python-fullmoon as a dependency, and do full moon detection. 😊 Seems to me like it would work out of the box with the is_full_moon() function which appears to return True for approximately ±12 hours from the maximum moon phase. So around 1 full day every month.