test: benchmark decoder

[abemedia]

Copy decoder benchmark to decoder package to run on CI.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.49%. Comparing base (bce915f) to head (23beae3).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #227   +/-   ##
=======================================
  Coverage   98.49%   98.49%           
=======================================
  Files          24       24           
  Lines         732      732           
=======================================
  Hits          721      721           
  Misses          6        6           
  Partials        5        5           

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[github-actions]

Benchmark Results

decoder

goos: linux
goarch: amd64
pkg: github.com/abemedia/go-don/decoder
cpu: AMD EPYC 7763 64-Core Processor                
          │    after    │
          │   sec/op    │
Decoder-4   766.3n ± 2%

          │   after    │
          │    B/op    │
Decoder-4   176.0 ± 0%

          │   after    │
          │ allocs/op  │
Decoder-4   3.000 ± 0%