Fetches the index of a given feature tag in the specified face's GSUB table or GPOS table, underneath the specified script and language.
| face |
Face to work upon |
| table_tag |
|
| script_index |
The index of the requested script tag |
| language_index |
The index of the requested language tag |
| feature_tag |
Tag of the feature tag requested |
| feature_index |
The index of the requested feature |
|
`true` if the feature is found, `false` otherwise |