Create: Hostile Skies

Added

• Ships and structures now load through the datapack resource system. Custom ships can be added via datapacks without modifying the mod
• /hostileskies ships command to list all registered ships
  • An in depth guide can be found on the github page (CUSTOM_SHIPS.md)

Changed

• Ship IDs are now namespaced (e.g. hostile_skies:karve_t1). Existing worlds are fully compatible
• Structure loading uses vanilla's StructureTemplateManager instead of classpath loading