Fix readonly array type error with Array.isArray

[Didericis]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything or linked relevant results below
• I made sure the docs are up to date
• I included tests (or that’s not needed)

Description of changes

Fixes type narrowing when using Array.isArray with read only arrays.

(Builds are currently failing/this fixes it. Documented in this issue -> #17)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6cc848a) to head (a8f3119).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #18   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines          181       145   -36     
=========================================
- Hits           181       145   -36     

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[github-actions]

Hi! This was closed. Team: If this was merged, please describe when this is likely to be released. Otherwise, please add one of the no/* labels.