exportToObj function
Writes document as OBJ (with its .mtl beside it, when the document
names a material), reads the result back and compares — held to
ObjWriter.decimals' own precision rather than 0.0, since a decimal
text format rounds on the way out by design.
Implementation
Future<ExportReport> exportToObj(
ModelDocument document, {
String name = 'model',
}) => exportChecked(document, const ObjModelWriter(), name: name);