#47 frontend-dev runs yarn install on docker-compose up

[martinjrobins]

Fixes #47

[mjaquiery]

Looks good -- do you know if it'll also manage to yarn install when running the production deployment? Can you test that if necessary and then merge when you're happy, please?

[martinjrobins]

in a production env node_modules is in /usr/share/nginx/html so this won't be a problem. In fact I'm not sure why this mapping is in the prod docker-compose file:

    volumes:
     - ./frontend:/app

Should this be only in the dev docker-compose?

[martinjrobins]

I tried prod deploy and seems to work ok, merging....