Add new music tracks to the sound directory

- Added cosmic_unicorns.ogg
- Added funky_eldritch.ogg
- Added meditative_beings.ogg
- Added owniverse_main_theme.ogg

These tracks enhance the audio experience of the project.

world/owniverse/civilization_state.gd

@@ -231,4 +231,4 @@ static func effective_span(world, target: Dictionary, id: String, rules: Diction
     var weighted: Variant = population
     for home in target.civilization_homes.get(id, {}):
         weighted = E.add(weighted, E.multiply(target.civilization_homes[id][home], (E.subtract(E.maximum(0, world.catalog.entities[home].civ_bonus), 1))))
-    return (E.divide(E.multiply(base, population), weighted) if E.gt(weighted, 0) else base)
+    return (E.mul_div(base, population, weighted) if E.gt(weighted, 0) else base)