There's no simple, cross-platform way to register protocol handlers in Electron. Every OS requires a different solution. This seems like something that Electron should smooth over.

There's already a W3C API for this: [`Navigator.registerProtocolHandler`](https://developer.mozilla.org/en-US/docs/Web/API/Navigator/registerProtocolHandler). Can Electron implement it?

atom/browser/browser_linux.cc
#include "atom/browser/browser.h"
#include <stdlib.h>
#include "atom/browser/native_window.h"
#include "atom/browser/window_list.h"
#include "atom/common/atom_version.h"
#include "brightray/common/application_info.h"
namespace atom {
void Browser::Focus() {