feat: improve get one byte performance

[fengmk2]

use getByte() instead of get()

[fengmk2]

before

after

[fengmk2]

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@7dd0a0c). Click here to learn what that means. The diff coverage is 100%.

@@            Coverage Diff            @@
##             master      #29   +/-   ##
=========================================
  Coverage          ?   96.24%           
=========================================
  Files             ?        2           
  Lines             ?      346           
  Branches          ?       79           
=========================================
  Hits              ?      333           
  Misses            ?       13           
  Partials          ?        0

Impacted Files	Coverage Δ
lib/byte.js	96.23% <100%> (ø)

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[fengmk2]

呃，为何没有继续推进。。 @gxcsoccer