Add CustomEvent polyfill and fire drop event in load dialog

[dnlbaines]

This adds a polyfill to allow us to create CustomEvents. A CustomEvent is now fired when a file is dropped into the load dialog.

[microbit-carlos]

@danbai02 Did you test this in IE10?
https://developer.microsoft.com/en-us/microsoft-edge/tools/vms/

[dnlbaines]

@danbai02 Did you test this in IE10?
https://developer.microsoft.com/en-us/microsoft-edge/tools/vms/

I have not, I develop in an Ubuntu VM which makes this harder. I usually use IETab but that does not seem to work with drag and drop.

[microbit-carlos]

Can you run it in an IE10 vm? You can probably just download the zip file inside the windows VM and test it from there: https://github.com/danbai02/PythonEditor/archive/master.zip
With the default networking in virtualbox I normally serve from the host and then in the VM just go to the host ip (easy to spot using ifconfig or ipconfig) , although i am not sure if that would still work if you are serving from a different vm.

[dnlbaines]

Can you run it in an IE10 vm? You can probably just download the zip file inside the windows VM and test it from there: https://github.com/danbai02/PythonEditor/archive/master.zip
With the default networking in virtualbox I normally serve from the host and then in the VM just go to the host ip (easy to spot using ifconfig or ipconfig) , although i am not sure if that would still work if you are serving from a different vm.

Confirmed working in IE10.

[microbit-carlos]

Great, thanks @danbai02!