Document empty printResolutions

Author: manisandro

src/configuration/ThemesConfiguration.md

@@ -142,7 +142,7 @@ The format of the theme definitions is as follows:
 | `"attributionUrl": "<URL>",`                    | Optional, link associated to the attribution                                      |
 | `"scales": [<Scale denominators>],`             | List of denominators of allowed map scales. If omitted, defaults to `defaultScales`. |
 | `"printScales": [<Scale denominators>],`        | List of denominators of allowed print scales. If omitted, defaults to `defaultPrintScales`. |
-| `"printResolutions": [<DPIs>],`                 | List of available print resolutions. If omitted, defaults to `defaultPrintResolutions`. |
+| `"printResolutions": [<DPIs>],`                 | List of available print resolutions. If an empty list, resolutions are freely choseable. If omitted, defaults to `defaultPrintResolutions`. |
 | `"printGrid": [`                                | List of grid scale-dependent grid intervals to use when printing. If omitted, defaults to `defaultPrintGrid`. |
 | `⁣  {"s": <Scale1>, "x": <Width1>, "y": <Height1>},` | Keep this list sorted in descending order by scale denominator.           |
 | `⁣  {"s": <Scale2>, "x": <Width2>, "y": <Height2>}`  | In this example, `{x: <Width2>, y: <Height2>}` will be used for `<Scale1> > Scale >= <Scale2>`. |