fix(manifests): split YAML using reader

[hiddeco]

This is an alternative approach to #305, to solve the issues described in #278 and #294 using a YAML reader that properly understands YAML document separators.

[netlify]

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Name	Link
🔨 Latest commit	82afa15
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[codecov]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Project coverage is 29.72%. Comparing base (da4f365) to head (82afa15).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/manifests/manifests.go	77.77%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #315      +/-   ##
==========================================
+ Coverage   29.58%   29.72%   +0.14%     
==========================================
  Files          23       23              
  Lines        1724     1729       +5     
==========================================
+ Hits          510      514       +4     
- Misses       1137     1138       +1     
  Partials       77       77              

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