I don't know if I can do that, but my intention is just to help, sorry about anything.
I noticed that there is no update for a long time so I decided to help anyone who needs it.
First of all, we have to update the "config" file:

We have to add the follow category:

  "Public CargoShip Announcements": {
    "Despawn": true,
    "Despawn Banner Color": "Red",
    "Despawn Text": "The CargoShip has left.",
    "Despawn Text Color": "White",
    "Spawn": true,
    "Spawn Banner Color": "Red",
    "Spawn Text": "CargoShip Inbound!",
    "Spawn Text Color": "Orange"
  },

If necessary, use a json validator here. Now in code ("cs" file):

Look for:

public bool helicopterSpawnAnnouncement { get; private set; } = true;

... and paste this above:

        //CargoShip Announcements
        public bool cargoshipSpawnAnnouncement { get; private set; } = true;
        public bool cargoshipDespawnAnnouncement { get; private set; } = false;
        public string cargoshipSpawnAnnouncementText { get; private set; } = "CargoShip Inbound!";
        public string cargoshipDespawnAnnouncementText { get; private set; } = "The CargoShip has left.";
        public string cargoshipSpawnAnnouncementBannerColor { get; private set; } = "Red";
        public string cargoshipSpawnAnnouncementTextColor { get; private set; } = "Orange";
        public string cargoshipDespawnAnnouncementBannerColor { get; private set; } = "Red";
        public string cargoshipDespawnAnnouncementTextColor { get; private set; } = "White";

Look for:

helicopterSpawnAnnouncement = GetConfig("Public Helicopter Announcements", "Spawn", true);

... and paste this above:

            //CargoShip Announcements
            cargoshipSpawnAnnouncement = GetConfig("Public CargoShip Announcements", "Spawn", true);
            cargoshipSpawnAnnouncementText = GetConfig("Public CargoShip Announcements", "Spawn Text", cargoshipSpawnAnnouncementText);
            cargoshipSpawnAnnouncementTextColor = GetConfig("Public CargoShip Announcements", "Spawn Text Color", cargoshipSpawnAnnouncementTextColor);
            ConvertTextColor(cargoshipSpawnAnnouncementTextColor, true);
            if (!ConvertedTextColor)
            {
                ConvertedTextColor = true;
                PrintWarning("\"Public CargoShip Announcements - Spawn Text Color: " + cargoshipSpawnAnnouncementTextColor + "\" is not a valid color, resetting to default.");
                Config["Public CargoShip Announcements", "Spawn Text Color"] = "Orange";
                ConfigUpdated = true;
            }
            cargoshipDespawnAnnouncement = GetConfig("Public CargoShip Announcements", "Despawn", cargoshipDespawnAnnouncement);
            cargoshipDespawnAnnouncementText = GetConfig("Public CargoShip Announcements", "Despawn Text", cargoshipDespawnAnnouncementText);
            cargoshipDespawnAnnouncementBannerColor = GetConfig("Public CargoShip Announcements", "Despawn Banner Color", cargoshipDespawnAnnouncementBannerColor);
            ConvertBannerColor(cargoshipDespawnAnnouncementBannerColor, true);
            if (!ConvertedBannerColor)
            {
                ConvertedBannerColor = true;
                PrintWarning("\"Public CargoShip Announcements - Despawn Banner Color: " + cargoshipDespawnAnnouncementBannerColor + "\" is not a valid color, resetting to default.");
                Config["Public CargoShip Announcements", "Despawn Banner Color"] = "Red";
                ConfigUpdated = true;
            }
            cargoshipDespawnAnnouncementTextColor = GetConfig("Public CargoShip Announcements", "Despawn Text Color", cargoshipDespawnAnnouncementTextColor);
            ConvertTextColor(cargoshipDespawnAnnouncementTextColor, true);
            if (!ConvertedTextColor)
            {
                ConvertedTextColor = true;
                PrintWarning("\"Public CargoShip Announcements - Despawn Text Color: " + cargoshipDespawnAnnouncementTextColor + "\" is not a valid color, resetting to default.");
                Config["Public CargoShip Announcements", "Despawn Text Color"] = "White";
                ConfigUpdated = true;
            }

Look for this method:

void OnEntitySpawned(BaseNetworkable entity)

... and update:

        void OnEntitySpawned(BaseNetworkable entity)
        {
            if (helicopterSpawnAnnouncement && entity is BaseHelicopter)
            {
                CreateAnnouncement(helicopterSpawnAnnouncementText, helicopterSpawnAnnouncementBannerColor, helicopterSpawnAnnouncementTextColor);
            }
            
            if (stockingRefillAnnouncement && entity is XMasRefill)
            {
                CreateAnnouncement(stockingRefillAnnouncementText, stockingRefillAnnouncementBannerColor, stockingRefillAnnouncementTextColor);
            }
            
            if (cargoshipSpawnAnnouncement && entity is CargoShip)
            {
                CreateAnnouncement(cargoshipSpawnAnnouncementText, cargoshipSpawnAnnouncementBannerColor, cargoshipSpawnAnnouncementTextColor);
            }
        }

Look for method:

void OnEntityKill(BaseNetworkable entity)

... and update:

        void OnEntityKill(BaseNetworkable entity)
        {
            if (entity is BaseHelicopter)
            {
                var entityNetID = entity.net.ID;
                timer.Once(2, () =>
                {
                    if (HeliNetIDs.Contains(entityNetID))
                        HeliNetIDs.Remove(entityNetID);
                    else if (helicopterDespawnAnnouncement)
                        CreateAnnouncement(helicopterDespawnAnnouncementText, helicopterDespawnAnnouncementBannerColor, helicopterDespawnAnnouncementTextColor);
                });
            }
            if (entity is CargoShip)
            {
                if (cargoshipDespawnAnnouncement)
                    CreateAnnouncement(cargoshipDespawnAnnouncementText, cargoshipDespawnAnnouncementBannerColor, cargoshipDespawnAnnouncementTextColor);
            }
        }

..and ready, done!

Nice one. That will work for people that want to add it in until I get my partial rewrite update finished with all the missing events.

Just to let you know, I will be working on this very shortly now I've finished the command system rewrite (along with other missing event announcements).

All missing event announcements including this one have been added in the latest update just uploaded.

Ooooh juicy update! Thanks!