perf: migrate bytes.Buffer to strings.Builder for micro optimization

[aldy505]

Closes #4

[codecov-commenter]

Codecov Report

Merging #9 (3e4261d) into master (f1008bd) will increase coverage by 2.13%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master        #9      +/-   ##
===========================================
+ Coverage   97.86%   100.00%   +2.13%     
===========================================
  Files           9         9              
  Lines         281       275       -6     
===========================================
  Hits          275       275              
+ Misses          6         0       -6     

Impacted Files	Coverage Δ
internal.go	100.00% <ø> (+54.54%)	⬆️
create.go	100.00% <100.00%> (ø)
has.go	100.00% <100.00%> (ø)
upsert.go	100.00% <100.00%> (ø)

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