`compare_vars` to add referential footnotes when not enough sample size

[cicdguy]

Currently it just suppresses the warnings or does not show any result. Better would be to

• show NA and then have a footnote explaining that here the sample size was not sufficient to compute any p-value
• show the p-value and have a footnote with the warning message.

Provenance:

Creator: danielinteractive

[cicdguy]

@anajens fyi

Provenance:

Creator: danielinteractive