I doubt if glass is resistant to items sticking to it.
I have a need to park my car under an ornamental Maple tree and now (in the southern hemisphere) it is sheading leaves et al.
I need to clean the windscreen/windshield of my vehicle each day when I drive it out onto the street.
I am of the opinion that, if you wish to enjoy the tree, you will need to put up with the problems that it imposes.
You now find it necessary to have your gutters cleaned on a regular basis. The "extra" cleaning of a skylight should, surely, be a minimal consideration.