Use npx degit Instead Of polywrap create #1845

I propose we use degit instead of polywrap create, as they effectively function the same way. This means we maintain less code, and can use a popular widely-used package: https://www.npmjs.com/package/degit

In this future it could be pwr degit instead of npx degit. Also for a nice UX, we could keep the name polywrap create but just use degit underneath.