Fixes a metric pantload of spelling errors, bad grammar, incorrect punctuation, and malapropisms in monsters.json.

I started by trying to fix all the it's/its confusion and realized that there was a LOT more than that to fix.

I've not bothered to change most of the instances of really abnormal phrasing and the spots where it trips all over itself trying to use all the thesaurus words that it possibly can; this primarily focuses on making it so that those of us who have an inner Grammar Nazi don't tear all of our hair out when we read the monsters' descriptions.