fix(serve-static): use application/octet-stream if the mime type is not detected

[usualoma]

Currently, if the mimeType could not be detected, the Content-Type is not set, so it falls back to “text/plain”. There may be cases where “text/plain” is acceptable, but I don't think it is appropriate for binary data to be returned as "text/plain", so I think it should be "application/octet-stream”. Even on general web servers, the default is "application/octet-stream" for files that cannot be detected from the file extension.

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.77%. Comparing base (0edb243) to head (ffe1407).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3415      +/-   ##
==========================================
- Coverage   95.78%   95.77%   -0.01%     
==========================================
  Files         155      155              
  Lines        9314     9310       -4     
  Branches     2771     2771              
==========================================
- Hits         8921     8917       -4     
  Misses        393      393              

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[yusukebe]

LGTM!

[yusukebe]

@usualoma

Thank you. You are right. It's should be application/octet-stream Merging.