Retrieve a factor with all label languages used in a specific xlsform. Used in the app to retrieve the language to consider based on the form
Examples
## With different language
fct_xlsfrom_language( xlsformpath = system.file("demo.xlsx",
package = "XlsFormUtil"))
#> [1] "English" "Tigirigna" "Amharic" "Oromiffa"
## without language
fct_xlsfrom_language( xlsformpath = system.file("KoBoXLSFormExamples.xlsx",
package = "XlsFormUtil"))
#> NULL