feat: embed code into markdown and keep everything in sync

[appleboy]

fix #190

[codecov-io]

Codecov Report

Merging #191 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #191   +/-   ##
=======================================
  Coverage   96.14%   96.14%           
=======================================
  Files          13       13           
  Lines         881      881           
=======================================
  Hits          847      847           
  Misses         26       26           
  Partials        8        8

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