Add instructions for Yarn 2.

I'm using Yarn 2, and when I use the `-r @cypress/instrument-cra` flag for `react-scripts start`, I'm greeted with this error (which does not exist when not providing the `-r` flag:

```
Error: Qualified path resolution failed - none of those files can be found on the disk.

Source path: ...\node_modules\react-scripts\config\webpack.config.js
Not found: ...\node_modules\react-scripts\config\webpack.config.js
Not found: ...\node_modules\react-scripts\config\webpack.config.js.js
Not found: ...\node_modules\react-scripts\config\webpack.config.js.json
Not found: ...\node_modules\react-scripts\config\webpack.config.js.node

Require stack:
- ...\.yarn\cache\@cypress-instrument-cra-npm-1.4.0-b310f2188a-1c404f1887.zip\node_modules\@cypress\instrument-cra\index.js
- internal/preload
at Function.external_module_.Module._resolveFilename (...\.pnp.cjs:35286:55)
at Function.external_module_.Module._load (...\.pnp.cjs:35085:48)
at Module.require (node:internal/modules/cjs/loader:1005:19)
at require (node:internal/modules/cjs/helpers:94:18)
at Object. (...\.yarn\cache\@cypress-instrument-cra-npm-1.4.0-b310f2188a-1c404f1887.zip\node_modules\@cypress\instrument-cra\index.js:41:24)
at Module._compile (node:internal/modules/cjs/loader:1101:14)
at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
at Module.load (node:internal/modules/cjs/loader:981:32)
at Function.external_module_.Module._load (...\.pnp.cjs:35135:14)
at Module.require (node:internal/modules/cjs/loader:1005:19)
```