fix(logging): do not use JSON.stringify to Error object

[Milly]

the result of JSON.stringify(new Error('msg')) is {}. pass the Error object to logger as it is.

[codecov-io]

Codecov Report

Merging #666 into master will increase coverage by 0.18%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #666      +/-   ##
==========================================
+ Coverage   82.40%   82.59%   +0.18%     
==========================================
  Files          15       15              
  Lines        2126     2126              
  Branches      509      448      -61     
==========================================
+ Hits         1752     1756       +4     
+ Misses        364      360       -4     
  Partials       10       10              

Impacted Files	Coverage Δ
src/plugins.ts	90.90% <100.00%> (+6.06%)	:arrow_up:

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