public B addMember(String memberName, ShapeId target) {
        return addMember(memberName, target, null);
    }
Adds a member to the builder.

@param memberName Member name to add.
@param target Target of the member.
@return Returns the builder.
smithy-model/src/main/java/software/amazon/smithy/model/shapes/NamedMembersShapeBuilder.java