Support for browsers that shipped with native Web Components

[motss]

leaflet-map is surprisingly still depending on the web components polyfill. It should provide support for native Web Components that shipped on Chrome and Opera.

[nhnb]

Yes, the demo pages include the polyfill. But I am not aware of a dependency from any component files on the webcomponent polyfill.

[motss]

@nhnb I'm using leaflet-map on Chrome with native Shadow DOM and without loading the web components polyfill. It is just broken without the polyfill and works fine with the polyfill which is why I said that it depends on the polyfill and none of files has that dependency.