docs: clarify that ICON can be a container path (#3371)

Author: itzg

docs/configuration/server-properties.md

@@ -197,14 +197,34 @@ New to [22W42A](https://www.minecraft.net/en-us/article/minecraft-snapshot-22w42
 
 ### Server icon
 
-A server icon can be configured using the `ICON` variable. The image will be automatically
-downloaded, scaled, and converted from any other image format:
+A server icon can be configured by setting the `ICON` variable to a URL to download or a container path. The image will be automatically downloaded (if a URL), scaled, and converted from any other image format:
 
-    docker run -d -e ICON=http://..../some/image.png ...
+!!! example
 
-The server icon which has been set doesn't get overridden by default. It can be changed and overridden by setting `OVERRIDE_ICON` to `TRUE`.
+    Using `docker run`:
+    
+    ```
+    docker run -d -e ICON=http://..../some/image.png ...
+    ```
+    
+    In compose file:
+    
+    ```yaml
+    environment:
+      ICON: http://..../some/image.png
+    ```
+    
+    Using a file from host filesystem:
+    
+    ```yaml
+    environment:
+      ICON: /icon.png
+      OVERRIDE_ICON: true
+    volumes:
+      ./icon.png:/icon.png
+    ```
 
-    docker run -d -e ICON=http://..../some/other/image.png -e OVERRIDE_ICON=TRUE...
+By default an existing `server-icon.png` file will not be replaced, that can be changed by setting `OVERRIDE_ICON` to "true".
 
 ### RCON
 
@@ -502,4 +522,4 @@ When using `docker run` from a bash shell, the entries must be quoted with the `
 | LOG_IPS                           | log-ips                           |
 | REGION_FILE_COMPRESSION           | region-file-compression           |   
 | BUG_REPORT_LINK                   | bug-report-link                   |
-| PAUSE_WHEN_EMPTY_SECONDS          | pause-when-empty-seconds          |
+| PAUSE_WHEN_EMPTY_SECONDS          | pause-when-empty-seconds          |