add mask click event handler function that allows overriding
add mask click event handler function that allows overriding

with that we can deny closing lightbox if it is still loading

Ben-Ho/koala-framework,nsams/koala-framework,kaufmo/koala-framework,yacon/koala-framework,Sogl/koala-framework,kaufmo/koala-framework,nsams/koala-framework,yacon/koala-framework,kaufmo/koala-framework,Ben-Ho/koala-framework,koala-framework/koala-framework,yacon/koala-framework,koala-framework/koala-framework,Sogl/koala-framework,nsams/koala-framework