Fix type definition of CustomEvent constructor

[takeohman]

Like #1837, I think CustomEvent constructor needs parameters.
The followings are links I checked.

https://dom.spec.whatwg.org/#interface-customevent
https://developer.mozilla.org/en/docs/Web/API/CustomEvent

http://html5index.org/DOM%20-%20EventInit.html
http://html5index.org/DOM%20-%20CustomEventInit.html

[msftclas]

Hi @takeohman, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. Real humans will now evaluate your PR.

TTYL, MSBOT;

[mhegazy]

thanks for the PR. As i mentioned in #1837 this file is auto generated from the IE definition files. this makes it easy for us to get an almost accurate DOM definitions without having to update them manually. We plan on updating how the dom typings are generated but for now, we can not make hand edits to this file. If you can log a separate issue, i can get it fixed in our script and update the file.

[mhegazy]

Can you file an issue to track the change

[takeohman]

mhegazy,

Thank you for your comment.
I made a new issue #2029 regarding this PR.
I hope what I did is OK.