0.6.4 release

Grammar handling has been refactored to support multiple grammar formats. Definitions must now be wrapped in a Grammar object with an explicit format selection. Currently supported formats: GBNF, JSONSchema.

// before:
.WithInferenceParams(new InferenceParams
{
Grammar = grammarText;
})

// after:
.WithInferenceParams(new InferenceParams
{
Grammar = new Grammar(grammarText, GrammarFormat.GBNF)
})