Gets the changes of the State array, left to right: each group with the state name before it. A group before any state
name, an unknown name and its groups, and an element that is neither a name nor a dictionary are skipped with a diagnostic.
public IReadOnlyList<PdfOcgStateChange> Changes { get; }
ISO 32000-2 §12.6.4.13, Table 217. A group may appear more than once; each change applies in order.