expose several additional constants related to PIRLS thresholds

[palday]

• add entry in NEWS.md
• after opening this PR, add a reference and run docs/NEWS-update.jl to update the cross-references.
• I've bumped the version appropriately

[codecov]

Codecov Report

❌ Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.65%. Comparing base (e31ae34) to head (2e7f120).

Files with missing lines	Patch %	Lines
src/generalizedlinearmixedmodel.jl	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #893   +/-   ##
=======================================
  Coverage   95.65%   95.65%           
=======================================
  Files          38       38           
  Lines        3726     3731    +5     
=======================================
+ Hits         3564     3569    +5     
  Misses        162      162           

Flag	Coverage Δ
current	95.33% <94.73%> (+<0.01%)	⬆️
minimum	95.54% <94.73%> (-0.05%)	⬇️
nightly	95.33% <94.73%> (+<0.01%)	⬆️

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[dmbates]

@palday This is a great idea - thank you for making this PR. Do you have any idea why the test on nightly is failing? I don't think the changes here should affect that test.

[palday]

@dmbates As far as I can tell, it was just an intermittent failure on that night's nightly. Everything is working now.