Fixing 'ReferenceError: moment is not defined' when booking a meeting.

[arithmetric]

This PR fixes an error I see from the Node server after I click to book a meeting with the demo.

/Users/joe/Work/Developer-Demo-Starter/app/server.js:128
    const meetingDate = moment(slot.start).format("DD MMM YYYY");
                        ^

ReferenceError: moment is not defined
    at /Users/joe/Work/Developer-Demo-Starter/app/server.js:128:25
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)