Promote exercise

[Hrenli]

So this fucking quarantine made us sit at home, gyms are closed etc etc. I was sitting for hours in front of the computer with my shoulders tired while looking at my hearthling chopping wood and thought that maybe just to teach the kids the benefits of physical activities it might be fun to add a _small_ chance of healing of some otherwise bad wounds (like nerve damage or whatnot) while doing stamina-intense activities outside. More like a gimmick (or "gymmick" even) really. The chance should be small enough not to be abused, but maybe as a slight incentive to not always use alts for labor. Could be an exp event too.