feat: FeeTokenPricerSet event (#324)

Author: gzeoneth

src/bridge/ISequencerInbox.sol

@@ -69,6 +69,9 @@ interface ISequencerInbox is IDelayedMessageProvider {
     /// @dev Owner set the buffer config.
     event BufferConfigSet(BufferConfig bufferConfig);
 
+    /// @dev Owner set the fee token pricer.
+    event FeeTokenPricerSet(address feeTokenPricer);
+
     function totalDelayedMessagesRead() external view returns (uint256);
 
     function bridge() external view returns (IBridge);

src/bridge/SequencerInbox.sol

@@ -880,6 +880,7 @@ contract SequencerInbox is DelegateCallAware, GasRefundEnabled, ISequencerInbox
         }
 
         feeTokenPricer = feeTokenPricer_;
+        emit FeeTokenPricerSet(address(feeTokenPricer_));
         emit OwnerFunctionCalled(6);
     }