### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Problem Description

Hi,

My team is trying to support universal linking in our application. Currently, in order to receive a handoff event from the browser, the application needs to listen to `continue-activity` event which provides `type` and `userInfo`. As per the Apple documentation [here](https://developer.apple.com/library/archive/documentation/UserExperience/Conceptual/Handoff/AdoptingHandoff/AdoptingHandoff.html#//apple_ref/doc/uid/TP40014338-CH2-SW10), the browser sends the app an `NSUserActivity` object with an `activityType` value of `NSUserActivityTypeBrowsingWeb`. The `webpageURL` property contains the URL the user was visiting, while the `userInfo` dictionary is empty. 

To provide a smooth handoff our application needs to know the URL the user is navigating from. Therefore, it would be great if the `webpageURL` parameter is exposed in `continue-activity` event. 


### Proposed Solution

The `NSUserActivity` object contains the `webpageURL` property which is set during the handoff process. 
I don't have any experience with Objective C but I believe the `webpageURL` property on the `userActivity` object can be allowed to pass [here](https://github.com/electron/electron/blob/da2baabb96161ea08a15820451f9374d63b4d678/shell/browser/mac/electron_application_delegate.mm#L161) to make it accessible.
https://github.com/electron/electron/blob/da2baabb96161ea08a15820451f9374d63b4d678/shell/browser/mac/electron_application_delegate.mm#L161


### Alternatives Considered

-

### Additional Information

The application needs to know the URL from where the user is navigating to provide a customized handoff experience. 
shell/browser/api/electron_api_app.h
const content::ChildProcessData& data,
      const content::ChildProcessTerminationInfo& info) override;
 private:
  void BrowserChildProcessCrashedOrKilled(
      const content::ChildProcessData& data,
      const content::ChildProcessTerminationInfo& info);
  void SetAppPath(const base::FilePath& app_path);
  void ChildProcessLaunched(int process_type,
                            int pid,
                            base::ProcessHandle handle,
                            const std::string& service_name = std::string(),
                            const std::string& name = std::string());
  void ChildProcessDisconnected(int pid);
  void SetAppLogsPath(gin_helper::ErrorThrower thrower,
                      absl::optional<base::FilePath> custom_path);
  
  base::FilePath GetPath(gin_helper::ErrorThrower thrower,
                         const std::string& name);
  void SetPath(gin_helper::ErrorThrower thrower,
               const std::string& name,
               const base::FilePath& path);
  void SetDesktopName(const std::string& desktop_name);
  std::string GetLocale();
  std::string GetLocaleCountryCode();
  void OnSecondInstance(const base::CommandLine::StringVector& cmd,
                        const base::FilePath& cwd);
  bool HasSingleInstanceLock() const;
  bool RequestSingleInstanceLock();
  void ReleaseSingleInstanceLock();
  bool Relaunch(gin::Arguments* args);