feat: added ruling event on the arbitrator side to help with subgraph indexing

Author: jaybuidl

contracts/src/arbitration/IArbitrator.sol

@@ -21,6 +21,14 @@ interface IArbitrator {
      */
     event DisputeCreation(uint256 indexed _disputeID, IArbitrable indexed _arbitrable);
 
+    /**
+     * @dev To be raised when a ruling is given.
+     * @param _arbitrable The arbitrable receiving the ruling.
+     * @param _disputeID ID of the dispute in the Arbitrator contract.
+     * @param _ruling The ruling which was given.
+     */
+    event Ruling(IArbitrable indexed _arbitrable, uint256 indexed _disputeID, uint256 _ruling);
+
     /**
      * @dev Create a dispute. Must be called by the arbitrable contract.
      * Must pay at least arbitrationCost(_extraData).

contracts/src/arbitration/KlerosCore.sol

@@ -866,6 +866,7 @@ contract KlerosCore is IArbitrator {
 
         (uint256 winningChoice, , ) = currentRuling(_disputeID);
         dispute.ruled = true;
+        emit Ruling(dispute.arbitrated, _disputeID, winningChoice);
         dispute.arbitrated.rule(_disputeID, winningChoice);
     }