Upgrade Stack + LTS

[brandon-leapyear]

✨ This is an old work account. Please reference @brandonchinn178 for all future communication ✨

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Can't use LTS 16 yet, because stack is unable to generate coverage reports: commercialhaskell/stack#3997

[codecov-commenter]

Codecov Report

Merging #40 into master will increase coverage by 1.84%.
The diff coverage is 94.80%.

@@            Coverage Diff             @@
##           master      #40      +/-   ##
==========================================
+ Coverage   85.98%   87.83%   +1.84%     
==========================================
  Files          10       11       +1     
  Lines         421      411      -10     
  Branches       31       27       -4     
==========================================
- Hits          362      361       -1     
+ Misses         49       40       -9     
  Partials       10       10              

Impacted Files	Coverage Δ
src/Data/Aeson/Schema/TH/Utils.hs	73.95% <0.00%> (-0.05%)	⬇️
src/Data/Aeson/Schema/Utils/Sum.hs	75.00% <75.00%> (ø)
src/Data/Aeson/Schema/Internal.hs	94.66% <98.03%> (+10.14%)	⬆️
src/Data/Aeson/Schema/Key.hs	100.00% <100.00%> (ø)
src/Data/Aeson/Schema/Show.hs	93.75% <100.00%> (-2.09%)	⬇️
src/Data/Aeson/Schema/TH/Schema.hs	90.90% <100.00%> (+0.13%)	⬆️
src/Data/Aeson/Schema/Utils/All.hs	100.00% <100.00%> (ø)

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