fix: handle nested layers with dot notation

[bartveneman]

closes #8

[codecov-commenter]

Bundle Report

Changes will increase total bundle size by 267 bytes (3.05%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
cssLayerTree-esm	3.4kB	267 bytes (8.54%) ⬆️

Affected Assets, Files, and Routes:

view changes for bundle: cssLayerTree-esm

Assets Changed:

Asset Name	Size Change	Total Size	Change (%)
css-*.js	267 bytes	3.4kB	8.54% ⚠️

Files in css-*.js:

• ./src/TreeNode.js → Total Size: 1.71kB

• ./src/index.js → Total Size: 4.2kB

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e6bb74c) to head (a342a6a).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #10   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          206       220   +14     
=========================================
+ Hits           206       220   +14     

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