Implement currency, shops, and enhanced NPC interaction system

world/lawold/npcs/breda.toml

@@ -3,3 +3,13 @@ description = "Breda is haughty in bearing, with thin auburn hair and narrow blu
 room = "lawold:well_market_trade_stalls"
 race = "race:human"
 base_attitude = "aggressive"
+
+[dialogue]
+greeting = "What do you want? I'm busy. Unless you have some teeth to sell?"
+keywords = { teeth = "I buy monster teeth. One silver each. No questions asked.", tools = "My tools aren't for sale, but I have some spares if you have the coin." }
+
+[shop]
+buys = ["junk", "teeth", "tool"]
+sells = ["town:small_hammer", "town:chisel"]
+markup = 1.2
+markdown = 0.5