github-electron: add missing remote.getCurrentWebContents()

API document is here:

https://github.com/atom/electron/blob/master/docs/api/remote.md#remotegetcurrentwebcontents

github-electron/github-electron.d.ts

@@ -1541,6 +1541,10 @@ declare module Electron {
 		 * @returns The BrowserWindow object which this web page belongs to.
 		 */
 		getCurrentWindow(): BrowserWindow;
+		/**
+		 * @returns The WebContents object of this web page.
+		 */
+		getCurrentWebContents(): WebContents;
 		/**
 		 * @returns The global variable of name (e.g. global[name]) in the main process.
 		 */