Fix typos in README.md

[QuinnWilton]

[QuinnWilton]

The "Why another typeclass?" section also seems like the text got cut-off partway through, but I'm not sure what its intended to say, so I left that unchanged: https://github.com/expede/rescue/pull/17/files#diff-b335630551682c19a781afebcf4d07bf978fb1f8ac04c6bf87428ed5106870f5R92

[QuinnWilton]

@QuinnWilton Tahnks fr fixig all of myy typos acros many projecst!!!11!1!

I laughed so hard when I saw this email come in 🤣

I added one more fix that jumped out to me while re-reading the changes! I also don't have maintainer access on this one, so you'll need to hit merge yourself this time 😅

[QuinnWilton]

@expede Bump in case this fell off your stack!