Presta valve stem reinforcement

Not quite a remix of the [Valve stabiliser for carbon road bike wheels](https://www.thingiverse.com/thing:149709) as I modeled it from scratch, but definitely an inspiration, so wanted to give the credit.

Sometimes a Presta nut doesn't sit quite right on a rim profile, generally because of a curve in the rim. I've printed RodLaird's design before, but I don't have carbon aero rims, so it doesn't fit _quite_ right. Working on a fat bike wheelset with a curved center channel, I thought of this