Fix types of wrapped Electron methods to return Promise

[andersk]

Fixes #878, fixes #998.

[VerteDinde]

@andersk Sorry it took so long for someone to see this 🙂 I merged your doc/type PR and I think I can reconcile the conflicts in the main definition file, but let me know if that seems reasonable and we can merge this one as well!

[andersk]

The PR you merged (#897) is not mine. Like I said there, this is a more complete fix. It was was intended to be merged instead of #897, not in addition to #897.

However, I’ve now resolved the conflicts so this can be applied on top.

[jlennox]

@andersk @VerteDinde Is there any update on this?

This would presumably fix an issue I am seeing:

.../node_modules/spectron/lib/spectron.d.ts:260:24 - error TS2694: Namespace 'Electron.CrossProcessExports' has no exported member 'RemoteMainInterface'.

260     electron: Electron.RemoteMainInterface;
                           ~~~~~~~~~~~~~~~~~~~