Add note that default launchSettings.json does not use port 5000, must be manually edited

[doingnz]

It would help newbies to tell them to edit the launchSettings.json file to set the port to 5000 to get this sample to run.

  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:5000/",
      "sslPort": 0
    }

[BrennanConroy]

Which sample specifically? There are many samples in this repo.