build: add Node 12 remove Node 11

[bcoe]

No description provided.

[codecov]

Codecov Report

Merging #520 into master will increase coverage by 3.69%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #520      +/-   ##
==========================================
+ Coverage   72.69%   76.38%   +3.69%     
==========================================
  Files           7        7              
  Lines         271      271              
  Branches       56       56              
==========================================
+ Hits          197      207      +10     
+ Misses         59       49      -10     
  Partials       15       15

Impacted Files	Coverage Δ
ts/src/index.ts	58.69% <0%> (+3.26%)	⬆️
ts/src/profiler.ts	89.44% <0%> (+4.34%)	⬆️

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