Support - values #4
Description
Positional - values are often used for stdin/stdout options. Currently, "-" is being treated explicitly as a "positional" & can't become the value of an arg unless defined with an explicit = (ie. --option=-) ref. https://github.com/darcyclarke/minargs/blob/main/index.js#L85-L90. When positionalValues=true then an arg set like --output - should set the value of output to "-" accordingly. This will require a major bump.