feat: add description

Author: MerlinEgalite

src/adapters/WstEthEthExchangeRateChainlinkAdapter.sol

@@ -13,6 +13,7 @@ import {ErrorsLib} from "../libraries/ErrorsLib.sol";
 /// @dev This contract should only be used as price feed for `ChainlinkOracle`.
 contract WstEthEthExchangeRateChainlinkAdapter is MinimalAggregatorV3Interface {
     uint8 public constant decimals = 18;
+    string public constant description = "wstETH/ETH exchange rate";
 
     IStEth public immutable ST_ETH;
 

test/WstEthEthExchangeRateChainlinkAdapterTest.sol

@@ -24,6 +24,10 @@ contract WstEthEthExchangeRateChainlinkAdapterTest is Test {
         assertEq(oracle.decimals(), uint8(18));
     }
 
+    function testDescription() public {
+        assertEq(oracle.description(), "wstETH/ETH exchange rate");
+    }
+
     function testDeployZeroAddress() public {
         vm.expectRevert(bytes(ErrorsLib.ZERO_ADDRESS));
         new WstEthEthExchangeRateChainlinkAdapter(address(0));