Upgrade to pnpm 8 #39
Description
We're currently assuming pnpm 7.x, but pnpm 8 has been out for a while and has a new lockfile format.
We've had cases where someone gets a new machine and installs pnpm and gets the latest version (8.x) and then the prepare script will do a pnpm install and the lockfile gets updated and confusion ensues.
We could stay on 7.x, but there are reasons to move forward to 8.x, so I will update the lockfile and update the GitHub Actions workflows to use pnpm 8 instead of 7.