been sitting on this branch forever but it seems to be working for me so might as well push it and see if it fixes anything

FEATURES:
new city-states (Aegina, Minsk and Mount Vernon)
new improvements (Sanctuary, Tsarkva and Tulip Field)

BUG FIXES:
it's been like a year since i last worked on this but hopefully smth got fixed

pls dont look at the civilopedia entries for the new stuff

Fixed an issue where Gedemo's Effigy Mound and Diquis Spheres improvements were not referenced correctly, causing crashes.

Changed the bonus given by the Consulate and Agency Headquarters buildings:

Consulate: +1 Influence Point per turn. Enemy Spy's level is reduced by 1 when targeting this District or adjacent Districts. Spies trained in this city receive the Smear Campaign promotion (Fabricate Scandal as if 2 levels more experienced). Receive +1 Spy capacity when constructing this building for the first time.

Agency Headquarters: +2 Influence Points per turn. Enemy Spy's level is reduced by 1 when targeting this District or adjacent Districts. Spies trained in this city receive the Disguise promotion (takes no time to establish in a city). Enables the Covert Ops Project.

Tweak to Országház Wonder:
Now requires an adjacent Diplomatic Quarter with a Foreign Affairs Office (in addition to a River)
Awards +2 Diplomatic Victory Points.

Implemented Tier 3 yield bonus system.
Replaced 3D art and icons for several buildings.
Further nerfs for citizen slots.

Nerfed citizen slots for most buildings.
Across-the-board nerfs for the Great Work-type policies.

Added support for Gedemo's Guayabo, Serpent Mound, and Su Nuraxi City-States.