Add: Chunk Operator #60

[ryo-kagawa]

#60
I added Chunk Operator
please check and review it.

[codecov]

Codecov Report

Merging #61 (ba48ae0) into master (b41b2b4) will decrease coverage by 0.91%.
The diff coverage is 97.48%.

@@            Coverage Diff             @@
##           master      #61      +/-   ##
==========================================
- Coverage   94.98%   94.06%   -0.92%     
==========================================
  Files          94       98       +4     
  Lines       15742    11884    -3858     
==========================================
- Hits        14952    11179    -3773     
+ Misses        765      679      -86     
- Partials       25       26       +1     

Impacted Files	Coverage Δ
stream/chunk.go	66.66% <66.66%> (ø)
internal/chunk/chunk.go	100.00% <100.00%> (ø)
internal/chunk/dispatcher.go	100.00% <100.00%> (ø)
internal/chunk/utils.go	100.00% <100.00%> (ø)
errors/codes.go	45.45% <0.00%> (-13.37%)	⬇️
stream/at.go	60.00% <0.00%> (-6.67%)	⬇️
stream/reduce.go	60.00% <0.00%> (-6.67%)	⬇️
stream/sort.go	66.66% <0.00%> (-6.07%)	⬇️
stream/removeduplicates.go	66.66% <0.00%> (-6.07%)	⬇️
stream/concat.go	77.77% <0.00%> (-4.05%)	⬇️
... and 92 more

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