Add tests for atoms input character count

[SaidShah]

• Related GitHub issue(s) linked in PR description
• Destination branch merged, built and tested with your changes
• Code formatted and follows best practices and patterns
• Code builds cleanly (no additional warnings or errors)
• Manually tested
• Automated tests are passing
• No decreases in automated test coverage
• Documentation updated (readme, docs, comments, etc.)
• Localization: No hard-coded error messages in code files (minimally in string constants)
• New component and/ or properties? Make sure to update storybook

Closes #12

[codecov]

Codecov Report

Merging #71 into main will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #71   +/-   ##
=======================================
  Coverage   25.66%   25.66%           
=======================================
  Files          51       51           
  Lines         900      900           
  Branches      209      209           
=======================================
  Hits          231      231           
  Misses        662      662           
  Partials        7        7           

Impacted Files	Coverage Δ
src/atoms/forms/input-character-count.tsx	100.00% <ø> (ø)

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