Created by: dstaley
This PR adds TypeScript as an optional peer dependency for react-scripts. This modification is necessary to get react-scripts working with Yarn v2, and will enable the TypeScript template for create-react-app to work with Yarn v2.
This PR uses the peerDependenciesMeta key, which signifies to Yarn that typescript is an optional dependency. npm will support the key in the future, in which case "typescript": "*" can be added to peerDependencies. Until that change is made, simply having peerDependenciesMeta will be enough for Yarn, and won't adversely impact users of npm.
Other relevant issues: yarnpkg/berry/pull/475
/cc @iansu