Wrote README

I created README.md and added some information to it.
I also added a sample linter program:

for sentence in sentences(doc) (
    length = char_count(doc, sentence)
    words = word_count(doc, sentence)
    has_hedging = or(
        contains(doc, sentence, "I think"),
        contains(doc, sentence, "I believe"),
        contains(doc, sentence, "perhaps"),
        contains(doc, sentence, "probably")
    )

    if and(
        gt(length, 100),
        gt(words, 15),
        has_hedging
    ) (
        sentence
    )
)