[DOCUMENTATION] Clarify getting started documentation regarding port …

…number used in pre-built Docker image. (#313)

docs/getting_started/docker.md

@@ -13,6 +13,10 @@ volume=$PWD/data  # share a volume with the container as a weight cache
 docker run --gpus all --shm-size 1g -p 8080:80 -v $volume:/data \
     ghcr.io/predibase/lorax:latest --model-id $model
 ```
+!!! note
+
+    The LoRAX server in the pre-built Docker image is configured to listen on port 80 (instead of on the default port number, which is 3000).
+
 !!! note
 
     To use GPUs, you need to install the [NVIDIA Container Toolkit](https://docs.nvidia.com/datacenter/cloud-native/container-toolkit/install-guide.html). We also recommend using NVIDIA drivers with CUDA version 11.8 or higher.