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
static_cast<AtomBrowserClient*>(AtomBrowserClient::Get())->set_delegate(this);
  Browser::Get()->AddObserver(this);
  content::GpuDataManager::GetInstance()->AddObserver(this);
}
App::~App() {
  static_cast<AtomBrowserClient*>(AtomBrowserClient::Get())->set_delegate(
      nullptr);
  Browser::Get()->RemoveObserver(this);
  content::GpuDataManager::GetInstance()->RemoveObserver(this);
}
void App::OnBeforeQuit(bool* prevent_default) {
  *prevent_default = Emit("before-quit");
}
void App::OnWillQuit(bool* prevent_default) {
  *prevent_default = Emit("will-quit");
}
void App::OnWindowAllClosed() {
  Emit("window-all-closed");
}
void App::OnQuit() {
  int exitCode = AtomBrowserMainParts::Get()->GetExitCode();
  Emit("quit", exitCode);
  if (process_singleton_.get()) {
    process_singleton_->Cleanup();
    process_singleton_.reset();
  }
}
void App::OnOpenFile(bool* prevent_default, const std::string& file_path) {