I modified the Makevars files to allow OpenMP usage. The geojsonR package is not parallelized, however the Armadillo library uses OpenMP internally to improve the execuction time of the functions.
I added the merge_files function.
I added the FROM_GeoJson_Schema function. This function is appropriate when the property-names do not match exactly the RFC 7946 specification ( for instance if the geometry-object-name appears as location, as is the case sometimes in mongodb queries ). This way one can avoid unnecessary errors when reading geojson files/strings.
I added a Vignette and corrected mistakes of the examples in the documentation