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/api/atom_api_app.cc
#include "atom/browser/api/atom_api_app.h"
#include <string>
#include <vector>
#include "atom/browser/api/atom_api_menu.h"
#include "atom/browser/api/atom_api_session.h"
#include "atom/browser/api/atom_api_web_contents.h"
#include "atom/browser/atom_browser_context.h"
#include "atom/browser/atom_browser_main_parts.h"
#include "atom/browser/browser.h"
#include "atom/browser/login_handler.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/net_converter.h"