re-support stream mode

[Kanahiro]

• toBuffer() takes about 30ms
• streaming takes about 50ms

streaming is slower than about 20ms but it may compensate in downloading.

[codecov]

Codecov Report

Attention: Patch coverage is 30.43478% with 96 lines in your changes missing coverage. Please review.

Project coverage is 58.09%. Comparing base (2771280) to head (45a2715).
Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/server/index.ts	15.15%	56 Missing ⚠️
src/index.ts	0.00%	23 Missing and 1 partial ⚠️
src/render/index.ts	40.74%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #110      +/-   ##
==========================================
- Coverage   58.76%   58.09%   -0.67%     
==========================================
  Files          19       19              
  Lines        1484     1575      +91     
  Branches       92       98       +6     
==========================================
+ Hits          872      915      +43     
- Misses        609      657      +48     
  Partials        3        3              

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