pairwise_caption: Pairwise comparison test expression
Description
This returns an expression containing details about the pairwise comparison
test and the p-value adjustment method. These details are typically
included in the ggstatsplot package plots as a caption.
Decides which pairwise comparisons to display.
Available options are "significant" (abbreviation accepted: "s") or
"non-significant" (abbreviation accepted: "ns") or
"everything"/"all". The default is "significant".