Document wmsOnly theme config setting

Author: manisandro

src/configuration/ThemesConfiguration.md

@@ -134,7 +134,8 @@ The format of the theme definitions is as follows:
 |-------------------------------------------------|-----------------------------------------------------------------------------------|
 | `"id": "<id>",`                                 | Theme identificator. Autogenerated if not specified.                              |
 | `"url": "<WMS URL>",`                           | The address of desired WMS served by QGIS Server.                                 |
-| `"mapCrs: "<EPSG code>",`                       | Optional, map projection, defaults to `defaultMapCrs`.                            |
+| `"mapCrs": "<EPSG code>",`                      | Optional, map projection, defaults to `defaultMapCrs`.                            |
+| `"wmsOnly": <true|false>`                       | Optional, whether the entry should only be configured as a WMS, and not as a theme. |
 | `"title": "<Custom title>",`                    | Optional, override WMS title.                                                     |
 | `"description": "<Description>",`               | Optional, an additional description to show below the theme title.                |
 | `"thumbnail": "<Filename>",`                    | Optional, image file in `assets/img/mapthumbs` (see [Viewer assets](ViewerConfiguration.md#viewer-asset)). If omitted, `<project_basename>.png` will be used if it exists below `assets/img/mapthumbs`, otherwise it is autogenerated via WMS GetMap. |