Consider migrating from yarn to npm

[dboreham]

While yarn was the shiny thing a few years ago and npm the drab old steam age tool, apparently the cool kids have switched back to npm (shiny now vs yarn which did a Python3 by introducing a new version incompatible with everyone's projects).

Therefore we should consider switching our builders and associated tooling to npm.

[AFDudley]

Sounds good please also consider https://pnpm.io/ and https://bun.sh