Consider switching from `npm` to `yarn`

[pyrello]

Motivation

I have mostly been using yarn as my node package manager on recent projects. When I originally pulled this down, I ran yarn install without even thinking about it. After realizing this was set up with npm, I ran npm install instead. Npm is much slower for me than yarn.

Proposed solution

• Run yarn install to generate yarn.lock and add that file.
• Remove 'package-lock.json` from the project.