Add support for yarn-path property

Yarn supports a `yarn-path` option, which allows you to point to a version of yarn within the repo. This makes it easy to ensure everyone working in the repo to be on the same version.

If this setting is specified, when `patch-package` copies over the `.yarnrc` to the temp folder, `yarn` will fail because it doesnt also copy over the yarn version. I think instead of copying the yarnrc, we can instead read, modify, and write the file to point to the correct old path. I will link the PR with this approach below. Let me know what you think!