Fixed the issue of pomodoro timer not running on mac because of winsound

[rohanprichard]

script name - pomodoro_timer.py

Fixing the pomodoro timer which was not working because of winsound

Issue no. - #894

Self Check(Tick After Making pull Request)

• [ ] This issue was assigned to me.
• [x] One Change in one Pull Request
• [x] My file is in proper folder (Name of folder should be in lowercase with no space in between) (E.g. meet_schedular)
• [x] I am following clean code and Documentation and my code is well linted with flake8.
• [x] I have added README.md and requirements.txt (Include version numbers too e.g. pandas==0.0.1) with my script
• [x] I have used REPO README TEAMPLATE (Necessary)
• [x] Just including required dependencies in requirements.txt (Don't include Python version too)