Provide option to change nlp.max_length

[dhicks]

I'm running into into the 1M character limit with a few texts that are only a bit over the length limit. It would be nice if I could pass higher values of nlp.max_length in through an argument somewhere, perhaps spacy_initialize().

[kbenoit]

Agreed!

Perhaps we could add a set of spacyr_options either via option() or something like quanteda_options() that define defaults that can be redefined the by the user, or reset prior to spacy_initialize(). Or passed as a list to spacy_initialize(..., options = list(spacyr_options()).