feat: ArbNativeTokenManager events (#349)

* feat: ArbNativeTokenManager events

* fix: address comments

Author: gzeoneth

src/precompiles/ArbNativeTokenManager.sol

@@ -11,6 +11,16 @@ pragma solidity >=0.4.21 <0.9.0;
  *         Available in ArbOS version 41
  */
 interface ArbNativeTokenManager {
+    /**
+     * @notice Emitted when some amount of the native gas token is minted to a NativeTokenOwner.
+     */
+    event NativeTokenMinted(address indexed to, uint256 amount);
+
+    /**
+     * @notice Emitted when some amount of the native gas token is burned from a NativeTokenOwner.
+     */
+    event NativeTokenBurned(address indexed from, uint256 amount);
+
     /**
      * @notice In case the caller is authorized,
      * mints some amount of the native gas token for this chain to the caller.