tweak(ped): add further documentation for SET_ENABLE_HANDCUFFS

[MadsLeander]

Adds further documentation for SET_ENABLE_HANDCUFFS and what it does.

Note: The example might be a little long, but I sincerely believe it's better than the following, as it showcases the native in an actual use case.

-- Sets handcuffs on the player's ped
SetEnableHandcuffs(PlayerPedId(), true)

If requested, I can make a short video showing/proving the example and my findings; I'm just too lazy to do it this second. Let me know if anything needs to be changed.