Add documentation for Province, Resource Node Data, Terrain Data, and Throne City

- Created a new document for Province detailing its characteristics and improvements.
- Added Resource Node Data documentation, including resource types, effects, and raw data tables.
- Introduced Terrain Data documentation, outlining terrain types, effects, and improvements available.
- Documented Throne City, highlighting its unique feature of providing extra gold income.

docs/Province.md

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+A tile in the game that represent an area of land. Contains [[Terrain Data]] and can contain [[Magic Material Data]], [[Resource Node Data]]. Based on the contained data, will have a series of Province Improvements that can be built on it when claimed by a city or outpost.