Fix option typo in README
Fix option typo in README

The actual implementation of the Swift short option command parsing used `-w` not `-sw`

paulsamuels/SBConstants,petester42/SBConstants,ashfurrow/SBConstants,raulriera/SBConstants,paulsamuels/SBConstants,orta/SBConstants,raulriera/SBConstants,petester42/SBConstants