Syllable count and or flesch-kincaid would be useful: https://github.com/daveross/flesch-kincaid.git

That flesch-kincaid needs to be updated.

const sentence = new Sentence({ text: 'tell me more', language: 'en' });
results in
`typeError: cannot read property 'findWord' of undefined'

This is because the language is En. The language should be case-insensitive

Conjugations for the verb "To Be"
http://conjugator.reverso.net/conjugation-english-verb-to%20be.html

http://conjugator.reverso.net/conjugation-english-verb-to%20give.html

Dictionary model should rely on LANGUAGE_NAMES constant to have a friendly name of the language.

"Can you help" returns a type is undefined.
guessSentenceTypeByPunctuation() should default to a type if none is found

add conjugations for , "to go"

http://conjugator.reverso.net/conjugation-english-verb-to%20go.html

I was
you were
he/she/it was
we were
you were
they were

In English (and probably other languages), a verb conjugation in written form is ambiguous without a pronoun.

A verb conjugation/inflection needs to be able to be marked as, ambiguous to signal to the sentence that it must do a second round of re-evaluation to determine correct conjugation and tense.

A verb dictionary should be able to take the word "went" and determine that this is the past tense of "to go".

http://conjugator.reverso.net/conjugation-english-verb-to%20say.html

In addition to regular conjugations, I should be able to add irregular verb conjugations

To go, to give, to be ... I should be able to add all of these to a verb dictionary

A function like this seems useful:

function getPersons(wordList) {
    const pronouns = wordList.filter((word) => word.partOfSpeech === 'pronoun');

    const first = pronouns.filter((pronoun) => pronoun.person === 1);
    const second = pronouns.filter((pronoun) => pronoun.person === 2);
    const third = pronouns.filter((pronoun) => pronoun.person === 3);

    return { first, second, third };
}

Grammar Dictionaries that are added to a language don't inherit the language setting that is put on the Language. They maybe should?

Or maybe not because that means we can mix and match grammarDictionaries across languages? IDK.

Think about it.