feat: make nesting available as countableCollection as well

[bartveneman]

follow-up of #468
related to #466

[codecov-commenter]

Bundle Report

Changes will increase total bundle size by 196 bytes (0.07%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
analyzeCss-esm	32.11kB	196 bytes (0.61%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: analyzeCss-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
css-*.js	196 bytes	32.11kB	0.61%

Files in css-*.js:

• ./src/index.js → Total Size: 33.84kB

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.87%. Comparing base (330af62) to head (cb773fb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #469   +/-   ##
=======================================
  Coverage   99.87%   99.87%           
=======================================
  Files          18       18           
  Lines        2365     2377   +12     
=======================================
+ Hits         2362     2374   +12     
  Misses          3        3           

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