Implemented optional pause/resume button in timer (#66)

[vijaykarthiktk]

Description:

This pull request implements the functionality discussed in issue #66, adding an optional pause/resume button to the timer. The pause/resume button is discreetly integrated within the timer ring. When enabled:

• Clicking the button pauses the timer, displaying the elapsed time and stopping further counting.
• Clicking again resumes the timer from the paused point.

When disabled, the timer behaves as usual without the button. A user setting allows enabling/disabling the pause/resume button functionality.

This functionality provides users with more control over the timer and improves the overall user experience.

The pull request includes discussions regarding the timer's behaviour after reaching the end while paused (e.g., keep elapsed time, reset to zero).

A video demonstrating the pause/resume button is attached:

https://github.com/MuhammadUsamaSiddiqui/circular_countdown_timer/assets/39937989/01ab7dff-b1ab-4d31-be14-f7af91600492