Use pnpm instead of yarn

[micash545]

Yarn v1 is outdated/deprecated

[jmattheis]

👍, but maybe we'll use npm instead as it much more common.

I don't accept PRs for this as reviewing this basically requires to do the migration again to check that there is no malicious stuff in the lockfile.

[eternal-flame-AD]

iirc pnpm supports a lossless lockfile conversion, but I will defer to jannis for whether to accept a PR at this point. I don't see a clear downside to yarn at this point except the telemetry thing (which I disabled for the project).

I tried pnpm migrate then pnpm i , the performance is about the same to me.