[FEATURE] Goal Timers for Custom Time Targets

Is your feature request related to a problem? Please describe.
I'm often frustrated when I need to manually track when a specific time goal is reached during my stopwatch sessions. I want a way to set a target (for example, 5 minutes or 10 laps) and get notified automatically when that target is achieved.

Describe the solution you'd like.
I would like the ability to set goal timers — customizable targets that trigger an animation, sound, or alert when reached.

Users can input a goal duration (e.g., 00:05:00).

When the stopwatch reaches the target, the app shows a visual highlight (like a pulse effect or confetti animation) and plays a short goal sound.

Optionally, allow multiple goals per session (for example, 1 min warm-up, 5 min main, 30 sec cooldown).

Additional context
This would make the stopwatch more useful for workouts, productivity sprints, or Pomodoro-style time tracking.