Native-looking menu bar item

[shreyasminocha]

Could you please add an option to make the menu item resemble the native date/time item? At the moment, my menu bar looks like this:

If the Itsycal menu bar item looked like:

I would have:

instead.

[shreyasminocha]

74. Very sorry for not having searched for closed issues prior to opening this issue. Consider adding this information to the readme.