Set clang-tidy config for MethodCase option

Previously this was falling back to FunctionCase, leading to inconsistent casing of class methods throughout the codebase. Applied to Item as an example.

Source/msg.cpp

@@ -701,7 +701,7 @@ DWORD OnRequestGetItem(const TCmd *pCmd, Player &player)
 			int ii = -1;
 			if (InDungeonBounds(position)) {
 				ii = abs(dItem[position.x][position.y]) - 1;
-				if (ii >= 0 && !Items[ii].KeyAttributesMatch(message.dwSeed, static_cast<_item_indexes>(message.wIndx), message.wCI)) {
+				if (ii >= 0 && !Items[ii].keyAttributesMatch(message.dwSeed, static_cast<_item_indexes>(message.wIndx), message.wCI)) {
 					ii = -1;
 				}
 			}