Update Docker notes

Author: geographika

docker/ReadMe.md

@@ -1,8 +1,18 @@
-# Creating the Docker Image
+# Overview
+
+This folder contains details on how to build the Docker images used for the workshop.
+Workshop attendees don't need to build these images themselves, they can simply use the built images.
+
+
+## Creating the Docker Image
 
 ```
 start "C:\Program Files\Docker\Docker\Docker Desktop.exe"
-cd C:\GitHub\getting-started-with-mapserver\docker
+
+# add --no-cache to the command below to force getting the latest code
+# can also test other repos / branches
+
+cd D:\GitHub\getting-started-with-mapserver\docker
 
 docker build `
     --tag "mapserver-workshop" `
@@ -11,11 +21,10 @@ docker build `
     --build-arg=MAPSERVER_REPO=https://github.com/mapserver/mapserver `
     .
 
-docker run -it --name mapserver-workshop -p 8080:8080 mapserver-workshop
+# docker run -it --name mapserver-workshop -p 8080:8080 mapserver-workshop
 
 docker tag mapserver-workshop geographika/mapserver-workshop
-
-docker login
+# docker login
 # geographika
 # docker images
 docker push geographika/mapserver-workshop
@@ -27,3 +36,34 @@ docker push geographika/mapserver-workshop
 docker start mapserver-workshop
 docker exec -it mapserver-workshop bash
 ```
+
+## Build the Demo Image
+
+This image contains both MapServer and all the MapServer workshop files so it can be deployed
+in the cloud. This is not required for the workshop itself, and users will use local files from the repository.
+
+```
+start "C:\Program Files\Docker\Docker\Docker Desktop.exe"
+# note parent path
+cd D:\GitHub\getting-started-with-mapserver
+
+docker build -f docker/Dockerfile.demo `
+    --tag "mapserver-workshop-demo" `
+    .
+
+# docker run -it --name mapserver-workshop-demo -p 8080:8080 mapserver-workshop-demo
+# http://localhost:8080/
+
+docker tag mapserver-workshop-demo geographika/mapserver-workshop-demo
+
+# docker login
+# geographika
+# docker push geographika/mapserver-workshop-demo
+
+# DigitalOcean
+doctl auth init
+doctl registry login
+docker tag mapserver-workshop-demo registry.digitalocean.com/geographika/mapserver-workshop-demo:latest
+docker push registry.digitalocean.com/geographika/mapserver-workshop-demo:latest
+
+```