Transform a PackedAtlas (or multiple PackedAtlases) into a TextAtlas (or multiple TextAtlases).
By default, the created text atlas files will be written to the current working directory.
The names of the new text atlas files will be the same as the input files, but with a '.txt'
extension instead of the usual '.atlas' extension.

To save as GeoJSON instead of using the TextAtlas format, use the '--geojson' option.
You can use line-delimited GeoJSON instead with '--ldgeojson'. Line-delimited GeoJSON
is much easier to read, since the regular GeoJSON format is all on one line. When using
GeoJSON, the new text atlas files will be created with the extension '.geojson'.
