- Introduced MarkedNetherPortal and MarkedNetherPortals classes to manage the marking and activation of Nether portals.
- Added PortalMarkStore for persistent storage of marked portals in YAML format.
- Created NetherPortalIgniter for a special item that allows marking portals in creative mode.
- Enhanced NetherAccess and NetherAccessListener to integrate the new portal marking system.
- Implemented commands and event handling for marking portals and managing their states.
- Added validation and chunk loading mechanisms to ensure proper portal functionality.