Fix broken compatibility of getNames

[danilofuchs]

This is an issue generated from this comment by @sebastien-prudhomme: #175 (comment)

Since #175, getNames is not following the expected behaviour.
It may return either a name or a names array. This can break integrations and may require weird code to handle this inconsistency. Perhaps we should add an options parameter: { alternativeNames?: boolean }.

By default, the library should return only the first name of the array (alternativeNames = false).

[ngdangtu-vn]

May I fix this issue? Today is late, so I will fix it and PR tomorrow.

[michaelwittig]

@ngdangtu-vn sounds good!