Firefly is now using yarn as a package manager

Thank you for bringing it up during the meeting. We have replaced npm package manager with yarn.

Installing yarn is a recently added prerequisite added to Firefly build process. The README on Firefly Github site was updated with this new requirement. Install yarn via npm: npm install yarn -g. The benefits of this update are the consistent versioning and the decrease in build time. On average, we see a 30-40 percent gain in build speed.