try to reduce warnings in examples and use examplesIf

[strengejacke]

Ref:

• Suppress (or attend to) warnings and messages in examples easystats#343
• Use #' @examplesIf roxygen directive over if() in the docs easystats#318

[codecov]

Codecov Report

Merging #616 (8f1df2b) into main (3b390de) will not change coverage.
The diff coverage is n/a.

❗ Current head 8f1df2b differs from pull request most recent head 4e063c0. Consider uploading reports for the commit 4e063c0 to get more accurate results

@@           Coverage Diff           @@
##             main     #616   +/-   ##
=======================================
  Coverage   51.92%   51.92%           
=======================================
  Files          84       84           
  Lines        5778     5778           
=======================================
  Hits         3000     3000           
  Misses       2778     2778           

Files Changed	Coverage Δ
R/looic.R	37.50% <ø> (ø)
R/model_performance.bayesian.R	68.61% <ø> (ø)
R/model_performance.rma.R	94.11% <ø> (ø)
R/r2_bayes.R	53.00% <ø> (ø)

[strengejacke]