Investigate single yarn workspace

[bollwyvl]

elevator pitch

See if it's possible to only need to do a single yarn install.

motivation

While the build time is dominated by webpack (and wrappers thereof), running yarn install 7 times is quite expensive.

design ideas

During env, discover all of the package.json files and build a work/package.json, and run a single yarn.

Sadly, a lot of things (in .js, .ts, .json, .toml and .py files) depend on files being deployed in a specific place in {cwd}/node_modules, so may require a lot of weird patching magic. Further, some packages run their own yarn install inside other scripts or elsewhere.