Rename nchains argument to ntrees

[jamesmbaazam]

This PR fixes #95.

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (0a28674) 98.63% compared to head (9ff192e) 98.06%.
Report is 7 commits behind head on main.

❗ Current head 9ff192e differs from pull request most recent head dfe2fc8. Consider uploading reports for the commit dfe2fc8 to get more accurate results

Files	Patch %	Lines
R/checks.R	57.14%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
- Coverage   98.63%   98.06%   -0.57%     
==========================================
  Files           8        8              
  Lines         511      516       +5     
==========================================
+ Hits          504      506       +2     
- Misses          7       10       +3     

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