graphql#320 suggested changing the
hard-coded port number in the example server so that it doesn't collide
with the test app.
Instead of that, let's use random port numbers, which will strictly
avoid any port collisions, including with apps that have nothing to do
with this repo, because the OS will assign an unused port.
Tested by simultaneously launching:
# In one terminal:
npm run start # prints: Started on http://localhost:51638/
# In another terminal:
npm run dev # prints: Started on http://localhost:51578/
Then hit both links and see they work.