Add implementation of Pomodoro Technique

[santosmarc14]

As a

user

I want to

use the pomodoro technique

To

to beat my procrastination ashah

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Acceptance Criteria

• [x] the timer should not stop when the user leaves the screen or the app (?)
• [x] a notification should be shown when the timer stops
• [x] basic functionality of the pomodoro technique ( pause timer, continue, the sets etc.)

[Jiseeeh]

inedit ko, edit mo kapag may naisip na ilalagay pa or aalisin @santosmarc14