Export type helper function and type optimization

[nonzzz]

CheckList

• Export a helper function defineCompressionOption.
• Type optimization.
• Add type-check test for overload function.

Relative

#58

@mengdaoshizhongxinyang

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.51%. Comparing base (5a16590) to head (f1147dd).
Report is 10 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##            master      #59      +/-   ##
===========================================
- Coverage   100.00%   90.51%   -9.49%     
===========================================
  Files            4        5       +1     
  Lines            4      527     +523     
  Branches         0      125     +125     
===========================================
+ Hits             4      477     +473     
- Misses           0       50      +50     

Files	Coverage Δ
src/compress.ts	100.00% <100.00%> (ø)
src/shared.ts	100.00% <100.00%> (ø)
src/tar.ts	79.12% <100.00%> (ø)
src/task.ts	97.22% <100.00%> (-2.78%)	⬇️
src/index.ts	94.55% <57.14%> (-5.45%)	⬇️