Update delete unread script to output unreads to be deleted and prompt for confirm deletion

Update delete unread script to output unreads to be deleted and prompt for confirm deletion

Part of debugging https://gitlab.com/gitlab-org/gitter/webapp/-/issues/2388

Parent MR: https://gitlab.com/gitlab-org/gitter/webapp/-/merge_requests/1871

$ node scripts/utils/delete-unreads-for-user-in-room.js --username EricGitterTester --room-uri MadLittleMods/trtrrtdshd

raven@2.6.0 alert: no DSN provided, error reporting disabled
2020-05-09T02:50:57.497Z - warn: ios push notification gateway (Prod) missing config, apn:certProd:undefined apn:keyProd:undefined
{ category: 'push-notifications' }
2020-05-09T02:50:57.502Z - warn: ios push notification gateway (Dev) missing config, apn:certDev:undefined apn:keyDev:undefined
{ category: 'push-notifications' }
2020-05-09T02:50:57.548Z - warn: ios push notification feedback (Dev) missing config, apn:certDev:undefined apn:keyDev:undefined
{ category: 'push-notifications' }
+ Are you sure you want to delete 2 unreads and 0 mentions? (yes/no)
{
        "chat": [
                "5eb61a8d965823db309f9f11",
                "5eb61a8d965823db309f9f12"
        ],
        "mention": []
}2020-05-09T02:50:58.067Z - info: Indices configured
{ category: 'persistence' }