Enhance Timer UI and User Engagement

[MAKROFREEK]

Description:
This pull request aims to improve the user experience of the Simple Timer Extension by enhancing the visual feedback and engaging the user when the timer is completed.

Changes:

Modified the timer's behavior to maintain a white color even after it's done, rather than changing to red. This provides a clearer indication of the timer completion without causing unnecessary distraction.

Updated the createTimerFinishedAlert() method to play three times with a 2-second interval between each alert. This change is intended to attract the user's attention effectively while ensuring a consistent user interface.

[MAKROFREEK]

First pull request ever, apologies--

I also added a Pomodoro functionality.