Entry points and quality of life improvements

• [conllformatter] Fixed an issue where SpaceAfter=No was not added correctly to tokens
• [conllformatter] Added ConllFormatter as an entry point, which means that you do not have to import
  spacy_conll anymore when you want to add the pipe to a parser! spaCy will know where to look for the CoNLL
  formatter when you use nlp.add_pipe("conll_formatter") without you having to import the component manually
• [conllformatter] Now adds the component constructor on a construction function rather than directly on the class
  as recommended by spacy. The formatter has also been re-written as a dataclass
• [conllformatter/utils] Moved merge_dicts_strict to utils, outside the formatter class
• [conllparser] Make ConllParser directly importable from the root of the library, i.e.,
  from spacy_conll import ConllParser
• [init_parser] Allow users to exclude pipeline components when using the spaCy parser with the
  exclude_spacy_components argument
• [init_parser] Fixed an issue where disabling sentence segmentation would not work if your model does
  not have a parser
• [init_parser] Enable more options when using stanza in terms of pre-segmented text. Now you can also disable
  sentence segmentation for stanza (but still do tokenization) with the disable_sbd option
• [utils] Added SpacyDisableSentenceSegmentation as an entry-point custom component so that you can use it in your
  own code, by calling nlp.add_pipe("disable_sbd", before="parser")