test: check TypeScript type definitions

[fengmk2]

https://github.com/SamVerschueren/tsd

[codecov]

Codecov Report

Merging #373 (6ddbd89) into master (dd75ea3) will decrease coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #373      +/-   ##
==========================================
- Coverage   93.17%   93.04%   -0.13%     
==========================================
  Files           6        6              
  Lines         820      820              
  Branches      223      223              
==========================================
- Hits          764      763       -1     
- Misses         56       57       +1     

Impacted Files	Coverage Δ
lib/urllib.js	96.07% <0.00%> (-0.16%)	⬇️

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