Introduce enums, custom exceptions, and KML validation

This release introduces key foundational features for the KML parser:

• GeometryType and RequiredElement enums to represent geometry types and required XML elements.
• KmlException, KmlParserException, and KmzExtractorException for more expressive and structured error handling.
• KmlValidator class to perform pre-validation of KML content before XML parsing.
• Integration of the validator into KmlParser::loadFromString().

These changes improve robustness and prepare the parser for more advanced validation and error reporting.

v1.0.0

⚠️ First Release Disclaimer

This package is in its early stages. Support for the KML format is still evolving as I continue to explore its structure and variations. Feedback and contributions are welcome!