Use neo-async insteaf of async

[mistic]

This PR replaces async with neo-async and improves the thread-loader performance a lot!

\CC @evilebottnawi

[codecov]

Codecov Report

Merging #54 into master will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff           @@
##           master     #54   +/-   ##
======================================
  Coverage    19.9%   19.9%           
======================================
  Files           7       7           
  Lines         432     432           
  Branches       74      74           
======================================
  Hits           86      86           
  Misses        305     305           
  Partials       41      41

Impacted Files	Coverage Δ
src/WorkerPool.js	28.98% <ø> (ø)	⬆️
src/worker.js	0% <0%> (ø)	⬆️

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