Describe the bug

After further research, it seems yarn.lock should be under source control after all. Therefore, we need to add it back in.

To Reproduce

See yarn.lock is missing from the release/2.2.0 branch.

Expected behavior

yarn.lock should be included in the repo.

Screenshots

n/a

Errors

n/a

Additional context

Per Yarn documentation:

All yarn.lock files should be checked into source control (e.g. git or mercurial). This allows Yarn to install the same exact dependency tree across all machines, whether it be your coworker’s laptop or a CI server.

Framework and library authors should also check yarn.lock into source control. Don’t worry about publishing the yarn.lock file as it won’t have any effect on users of the library.