Add optional XSD-driven schema mapping to ConvertXMLStringToJToken

[Copilot]

This change adds XSD support to Frends.JSON2.ConvertXMLStringToJToken so XML conversion can use schema information when present. With XSD input, conversion now preserves intended JSON shape for schema-defined repeating/object structures instead of relying only on XML instance shape.

• Task input contract

  • Added optional XSD parameter to Input for inline schema content used during conversion.

• Schema-aware conversion path

  • Kept existing behavior when XSD is not provided.
  • Added XSD-enabled path that:
    • compiles and validates XML against the provided schema,
    • enriches XML with Json.NET array hints based on schema occurrence metadata,
    • serializes to JToken with preserved array/object mapping semantics.

• Versioning and release notes

  • Bumped package version from 1.1.0 to 1.2.0 (second version number).
  • Added changelog entry describing XSD support and schema-based mapping behavior.

• Unit coverage

  • Added test for XSD-driven mapping to verify an element declared with maxOccurs="unbounded" is emitted as a JArray even when only one element exists in the XML payload.

var input = new Input
{
    XML = "<root><person id='1'><name>Alan</name></person></root>",
    XSD = @"<xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema'>
              <xs:element name='root'>
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name='person' maxOccurs='unbounded'>...</xs:element>
                  </xs:sequence>
                </xs:complexType>
              </xs:element>
            </xs:schema>"
};

var result = JSON.ConvertXMLStringToJToken(input);
// result.Jtoken["root"]["person"] is JArray