feat(useCountdown): add useCountdown hook

[JeongHwan-dev]

Overview

Add useCountdown hook: useCountdown is a React hook that manages a countdown timer with precise control. It provides functions to start, pause, resume, and reset the countdown. The hook tracks the current count value and supports both incrementing and decrementing modes.

Checklist

• Did you write the test code?
• Have you run yarn run fix to format and lint the code and docs?
• Have you run yarn run test:coverage to make sure there is no uncovered line?
• Did you write the JSDoc?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (c76f1fe) to head (3eab881).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #233   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           33        34    +1     
  Lines          839       884   +45     
  Branches       254       265   +11     
=========================================
+ Hits           839       884   +45     

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[seungrodotlee]

How about changing it to a more intuitive name? (e.g., useTimer)