Add first fuzzing test

[goccy]

fix #540

fuzz: elapsed: 5m45s, execs: 59696918 (169229/sec), new interesting: 696 (total: 1914)
fuzz: elapsed: 5m48s, execs: 60260185 (187751/sec), new interesting: 699 (total: 1917)
^Cfuzz: elapsed: 5m51s, execs: 60784500 (181145/sec), new interesting: 700 (total: 1918)
PASS
ok      github.com/goccy/go-yaml        351.456s

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 14.28571% with 42 lines in your changes missing coverage. Please review.

Project coverage is 77.60%. Comparing base (639f493) to head (785421b).

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #548      +/-   ##
==========================================
- Coverage   77.80%   77.60%   -0.20%     
==========================================
  Files          21       21              
  Lines        7086     7131      +45     
==========================================
+ Hits         5513     5534      +21     
- Misses       1200     1218      +18     
- Partials      373      379       +6