internal pop dens estimates in extdata json file to close #14

[mpadge]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.29%. Comparing base (4fad0aa) to head (e45311a).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
R/population-estimate.R	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
- Coverage   90.63%   89.29%   -1.34%     
==========================================
  Files          14       14              
  Lines        1142     1140       -2     
==========================================
- Hits         1035     1018      -17     
- Misses        107      122      +15     

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