Issue example requires yarn

[handeyeco]

Just thought I'd point out something that might be confusing to some.

In the README for the Issue example, there are instructions for both npm and yarn users:

    # npm users:
    npm start

    # yarn users:
    yarn start

When I went through the instructions without having yarn installed, I got an error:

$ npm start

> yarn run relay; concurrently --kill-others --names "react-scripts,relay" "react-scripts start" "yarn run relay --watch"

sh: yarn: command not found
[relay] /bin/sh: yarn: command not found
[relay] yarn run relay --watch exited with code 127

My point is, if yarn is required and yarn is not included as a dev dependency should the README include npm instructions at all?

Would recommend either:

• Removing npm examples from the README
• Adding yarn as a dev dependency

[kassens]

I think yarn run can be safely replaced with npm run here (if someone uses yarn, I think yarn automatically replaces npm with yarn for these scripts)