Add Eff, new Effect type to preserve async-sync

[mikearnaldi]

No description provided.

[codecov]

Codecov Report

Merging #180 into master will increase coverage by 0.00%.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master     #180   +/-   ##
=======================================
  Coverage   89.00%   89.01%           
=======================================
  Files          50       50           
  Lines        2402     2404    +2     
  Branches      309      309           
=======================================
+ Hits         2138     2140    +2     
  Misses        261      261           
  Partials        3        3           

Impacted Files	Coverage Δ
packages/effect/src/effect.ts	85.19% <50.00%> (+0.05%)	⬆️

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