Added "Chairdoro" to the "Utilities" category.

[chaiyikang]

[Insert URL to the app here.]
https://chairdoro.netlify.app/

[Explain what this app is about and why it should be included here.]
Chairdoro is an aesthetic pomodoro productivity timer, which allows you to alternate between fixed intervals of work and rest. These intervals can be fully customized. The app also comes with a to-do list, and comprehensive statistics tracking, integrated with the to-do list as well. However, progress is not saved across sessions and a free account has to be created to save progress. Also, there is a virtual cat which you can pet and feed. Doing work earns you more food to feed the cat.

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• I have read the Contribution guidelines and I am confident that my PR is suitable.
• This pull request has a descriptive title. For example, Add [App name], not Update readme.md or Added new entries.
• The app I added is not a duplicate.