Revamp, Optimize, Extend.

This release is a more feature packed one...
So what can be expected?

• The GPX parser has been revamped. It should be more efficient, delivering marginal improvements.
• Full Codable support across all GPX schema elements
• Optional error handling support
• Stable and optimised extensions
• Access control changes
• A GPXFix that makes sense
• Fully documented

Special Thanks to @mrfeet for contributing towards the project's tests

Hope you will enjoy this release of CoreGPX! 🎉