fix: schema validation

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

fix schema validation + some improvements

Breaking Changes

Should be not

Additional Info

No

[codecov]

Codecov Report

Merging #480 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #480      +/-   ##
==========================================
+ Coverage   88.47%   88.49%   +0.02%     
==========================================
  Files           5        5              
  Lines         425      426       +1     
  Branches       94       94              
==========================================
+ Hits          376      377       +1     
  Misses         47       47              
  Partials        2        2

Impacted Files	Coverage Δ
src/loader.js	89.24% <ø> (ø)	⬆️
src/index.js	87.85% <100%> (+0.05%)	⬆️

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