feat: expose syntax and type errors

[nieomylnieja]

Before submitting your PR, please confirm the following.

• Describe the purpose for which you created this PR.
  Solves Return structured errors #423
• Create test code that corresponds to the modification
  Unit tested yaml.AsTokenScopedError, tests added to error_test.go

[codecov-commenter]

Codecov Report

Merging #424 (1ee5296) into master (4653a1b) will increase coverage by 0.07%.
The diff coverage is 91.66%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #424      +/-   ##
==========================================
+ Coverage   76.02%   76.10%   +0.07%     
==========================================
  Files          13       13              
  Lines        4692     4716      +24     
==========================================
+ Hits         3567     3589      +22     
- Misses        866      868       +2     
  Partials      259      259              

[nieomylnieja]

Coming to think about, TypeError is equally useful as SyntaxError.
Maybe we could simply export the whole package? Would you consider that @goccy?
Then we wouldn't need to implement any As... extractor functions, anyone interested in reading these errors could simply do errors.As on their own.