add an async version of the WriteZipOutputStream benchmark

[Numpsy]

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[codecov]

Codecov Report

Merging #634 (f99b54d) into master (232d690) will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #634      +/-   ##
==========================================
+ Coverage   71.89%   71.94%   +0.05%     
==========================================
  Files          62       62              
  Lines        7667     7667              
==========================================
+ Hits         5512     5516       +4     
+ Misses       2155     2151       -4     

Impacted Files	Coverage Δ
...Code.SharpZipLib/Zip/Compression/DeflaterEngine.cs	87.45% <0.00%> (+0.33%)	⬆️
...ICSharpCode.SharpZipLib/BZip2/BZip2OutputStream.cs	78.74% <0.00%> (+0.33%)	⬆️

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