Ability to extend static Event interface

[Busyrev]

This is discussion question about extending builtin d.ts in projects.

In my particular case I would like to extend Event static intreface to add some static fields to Event(for special runtime that extends browser runtime).
I have found no way to do it. But for Array there is a way to use declaration merging because ArrayConstructor is separate named interface.
Here is example on playground

Tried it in #22946
@mhegazy thanks for answers in PR.

Question in general:

Find a way how to make any definition extendable without forking builtin d.ts files and changing them manually.

[mhegazy]

The answer to the general question is to make them classes (#574). there are some wrinkles here about what that entails though, callable constructors, and un-instantiate-able classes..

[mhegazy]

Is it required to be on the global Event? can you declare a wrapper?

[Busyrev]

In my case there already redefined Event(and some another browser api classes) in global by outer js code. This event does everything that original event does and some more. I can't simply extend Event, I should replace global Event defenition to more complicated defenition (declaration merging resolves issue as I showed in PR). I don't know any way to declare additional static fields to something that declared as 'declare Class'. Of cource I can rename extended Event to another name, but code quality became awful. Mutch better is just add special defenitions to project and define extended functionality for already available types.

[Busyrev]

Decided to fork d.ts files to project and edit them, exlude from lib section in tsconfig.