Remove yarn.lock from top-level

[jeffsee55]

Description

While all of our documentation indicates users should use the npm cli, we have a yarn.lock at the top-level of the monorepo, indicating that at some point that hasn't been the case. We should remove the yarn.lock to avoid confusion.

NOTE: this doesn't mean you can't use yarn while consuming these packages from outside the monorepo, this ticket is specifically about contributing to the monorepo.

I haven't run into an issue (that I know of) though I think the type of issues you'd see here are very subtle and probably hard to diagnose. There's a pretty good read of the potential issues here.