Add a longer serial console example

[benjaminleonard]

Would be useful for spotting issues like #1396 and #1048. Would mean we might also be able to add e2e tests for the scroll-to-top and bottom buttons.

[david-crespo]

We're going to change how the mock works because of the websockets endpoint (#1407) so that'll be a natural time to make the example longer.

[david-crespo]

I think we don't need this anymore now that we have the mock websocket endpoint.