Update readme and upgrade wrangler

[banyan]

@cometkim

Thanks for creating this library!
I made two changes.

1. Upgraded from wrangler1 to wrangler2
2. Have made the README a little clearer.
   • I thought this remote cache would be used more in CI. turborepo recommends adding .turbo directory to .gitignore file. So, rather than creating a .turbo/config.json file, I thought it would be easier to understand how to use it by explicitly passing the necessary options.

Please let me know if you have any requests regarding this changes.

[cometkim]

Thanks @banyan