FileAPI support

[maitredede]

Hi,

I think it can be a good idea to add the FileAPI objects : https://www.w3.org/TR/FileAPI/

Maybe in a extension assembly (and nuget package) ?

[paulbartrum]

There's no reason why this couldn't be added, but I'm focused on ECMAScript 6 right now, so it's quite far down my list of priorities. If you want to try implementing it yourself, let me know how you get on :-)