Gets the remainder of the base name after the first dot character. Note
that the name of this predicate is in plural form, unlike
which gets the remainder of the base name after the last dot character.
getExtension should be preferred over
getExtensions since the former pair is compatible
with the file libraries of other languages.
Note the slight difference between this predicate and
for example, for “file.tar.gz”, this predicate will have the result
getExtension will have the result “gz”.