Add monorepo package manager

[xujustinj]

We want a monorepo manager that would help us do the following things:

• from the root folder of the repo, install an npm package specifically in client or server

And these other things would be nice

• commit hooks to run tests and Prettier
• a new common package at the same level as client and server, which we can import in client and server by simply writing @client

Something like Lerna would work, but we're not sure if Lerna is what we want. See #24 for a related discussion.

For this ticket:

1. research the tradeoffs between different monorepo package managers for npm
2. write a spike on why we should choose X
3. add X to waterpark and make any necessary changes