refactor(utils/mime): make object and type commonality

[EdamAme-x]

In the previous state, we were writing the same thing twice. This PR defines it in only one place and then creates the type definition from the union of the object's values.

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.74%. Comparing base (4dd8b2b) to head (e863ad1).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3606      +/-   ##
==========================================
- Coverage   94.71%   89.74%   -4.97%     
==========================================
  Files         158      158              
  Lines        9555    10083     +528     
  Branches     2813     2887      +74     
==========================================
- Hits         9050     9049       -1     
- Misses        505     1034     +529     

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[yusukebe]

LGTM!

[yusukebe]

@EdamAme-x

Thanks! Looks good. Let's go.