PerpendicularOffset not parsed on LineSymbolizer (Geoserver SLD)

So using the GeoServer SLD parser on this XML:

```

Dashed line

SLD Cook Book: Offset line




#000000




#FF0000
5 2

5

```

I'm getting back:

```
{"TYPE_NAME":"SLD_1_0_0.StyledLayerDescriptor","version":"1.0.0","namedLayerOrUserLayer":[{"TYPE_NAME":"SLD_1_0_0.NamedLayer","name":"Dashed line","namedStyleOrUserStyle":[{"TYPE_NAME":"SLD_1_0_0.UserStyle","title":"SLD Cook Book: Offset line","featureTypeStyle":[{"TYPE_NAME":"SLD_1_0_0.FeatureTypeStyle","rule":[{"TYPE_NAME":"SLD_1_0_0.Rule","symbolizer":[{"name":{"namespaceURI":"http://www.opengis.net/sld","localPart":"LineSymbolizer","prefix":"sld","key":"{http://www.opengis.net/sld}LineSymbolizer","string":"{http://www.opengis.net/sld}sld:LineSymbolizer"},"value":{"TYPE_NAME":"SLD_1_0_0.LineSymbolizer","stroke":{"TYPE_NAME":"SLD_1_0_0.Stroke","cssParameter":[{"TYPE_NAME":"SLD_1_0_0.CssParameter","name":"stroke","content":["#000000"]}]}}},{"name":{"namespaceURI":"http://www.opengis.net/sld","localPart":"LineSymbolizer","prefix":"sld","key":"{http://www.opengis.net/sld}LineSymbolizer","string":"{http://www.opengis.net/sld}sld:LineSymbolizer"},"value":{"TYPE_NAME":"SLD_1_0_0.LineSymbolizer","stroke":{"TYPE_NAME":"SLD_1_0_0.Stroke","cssParameter":[{"TYPE_NAME":"SLD_1_0_0.CssParameter","name":"stroke","content":["#FF0000"]},{"TYPE_NAME":"SLD_1_0_0.CssParameter","name":"stroke-dasharray","content":["5 2"]}]}}}]}]}]}]}]}
```

So PerpendicularOffset is not parsed even though it's allowed by the GeoServer schema

https://github.com/geoserver/geoserver/commit/7d00473b6c7ddab81d331aec38dc2c301d1d7359

Or was the parser done before this change was done in the GeoServer schema?

https://github.com/geoserver/geoserver/commit/7d00473b6c7ddab81d331aec38dc2c301d1d7359

Start by comparing the GeoServer SLD schema change with the schema definition used for LineSymbolizer and the parser output shown in this issue. Trace how LineSymbolizer child elements are represented, then verify that PerpendicularOffset appears in the parsed result for the supplied XML example.

Written by the indexing model from the issue text.