Filament Spool Clip - improved

I have been using several filament clips I found of Thingivers (including some funny ones like dragons and crocodiles), but the rather simple [clip](https://www.thingiverse.com/thing:1194027), itself being a remix of [another clip](https://www.thingiverse.com/thing:39900), has always been my favorite. Easy and fast to print and works on many spools.

There were only two minor details I wanted to improve. The rather sharp edges tend ot cut into the plastic of sealed bags when deflated and after some time some of them wore out, loosing their tension on some spools.

Therefore I simply added some fillet for the edges (not too much so that they can still be printed without brim) and added a little slit to make them more elastic (inspired by another [remix](https://www.thingiverse.com/thing:3680172) of the above. Now they also work with slightly more brittle filaments, don't break easily and keep their tension.

And for spools with a broader rim, I added a larger XL version. Both clip