style macro - make trailing comma optional

[christolliday]

Thanks for this, the only issue is it is too permissive (allows any number of trailing commas,,,,,,,,) I think the way this is usually done is to add an alternate macro branch that calls the first, as in:

    ( $style_type:ident { $( $field:ident: $value:expr ) , * } ) => {
        style!(style_type { $($field: $value)* })
    };

update with this I'll merge it

[christolliday]

looks good thanks!