Fetches the index of the first language tag fom language_tags that is present
in the specified face's GSUB or GPOS table, underneath the specified script
index.
If none of the given language tags is found, false is returned and
language_index is set to the default language index.
Fetches the index of the first language tag fom language_tags that is present in the specified face's GSUB or GPOS table, underneath the specified script index.
If none of the given language tags is found, false is returned and language_index is set to the default language index.