Add docker docs

DOCKER.md

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+# Running Hytale Server with Docker
+
+It's recommended to run the Hytale server in a containerized environment like Docker for easier management and isolation. The server is new and there maybe be security issues or bugs that could cause harm on a production system, Docker helps mitigate these risks.
+
+If you want to use Docker after having the `/opt/Hytale/Server` configured, follow these steps:
+
+## Prerequisites
+
+- A working setup of the Hytale server. See the main [README](README.md) for installation instructions.
+- Docker and Docker Compose installed on your system. You can follow the official Docker [installation guide](https://docs.docker.com/get-started/get-docker/).
+
+## Setup
+
+1. **Create a `docker-compose.yml` file** in a convenient location (e.g., `/opt/Hytale/`):
+
+```yaml
+services:
+  hytale-server: 
+    image: eclipse-temurin:latest
+    container_name: hytale-server
+    restart: unless-stopped
+    working_dir: /opt/Hytale/Server
+    volumes:  
+      - /opt/Hytale/Server:/opt/Hytale/Server
+    ports:
+      - "5520:5520/udp"
+      - "5523:5523" # if you're using the https://github.com/nitrado/hytale-plugin-webserver plugin
+    command: java -jar HytaleServer.jar --assets Assets.zip --disable-sentry
+    stdin_open: true
+    tty: true
+```
+
+2. **Start the server**:
+```bash
+docker-compose up -d
+```
+
+3. **View server logs**:
+```bash
+docker-compose logs -f
+```
+
+4. **Stop the server**: 
+```bash
+docker-compose down
+```
+
+The result will be the same as running it natively, but now encapsulated in a Docker container.
+
+## Configuration Notes
+
+### Java Version
+
+The configuration uses `eclipse-temurin:latest` which may not always be compatible.  If you need a specific Java version, update the image tag: 
+
+```yaml
+image: eclipse-temurin:24-jre  # For Java 24
+# or
+image: eclipse-temurin:23-jre  # For Java 23
+```
+
+## Migration from Native Setup
+
+Since you're already running the server natively in `/opt/Hytale/Server`:
+
+1. Stop your native Java process
+2. Create the `docker-compose.yml` file
+3. Run `docker-compose up -d`
+4. Your server will continue using the same files and configuration
+
+No data migration is needed since the Docker container mounts your existing directory directly.