Missing dependencies in sub packages

[wmertens]

When using https://pnpm.js.org to install dependencies, the resulting tree is not flat like with npm 5. This has a number of advantages, but it also means that each package needs to properly declare its dependencies.

When using socketcluster 14, I also need to pull in

    "sc-broker": "^6.0.0",
    "sc-channel": "^1.2.0",
    "sc-hasher": "^1.0.1",

or it doesn't work. More annoyingly, the latest versions of these packages don't work with socketcluster 14, so I need to carefully match the versions.