#170 Revise GL on subaudible

[Martina Filosa]

The guidelines page on subaudible should be revised as per https://lsv.uky.edu/scripts/wa.exe?A2=MARKUP;51e1e7d7.2404&S= and following, adding more examples also from non Greek-Latin epigraphy. @sdigiulio will collect examples from Markup and draft a text.