bytes32 --> uint256 (#127)

Author: LeoPatOZ

src/protocol/taiko_alethia/TaikoAnchor.sol

@@ -21,7 +21,7 @@ struct BlockHeader {
     bytes extraData;
     bytes32 mixedHash;
     uint64 nonce;
-    bytes32 baseFeePerGas;
+    uint256 baseFeePerGas;
     bytes32 withdrawalsRoot;
     uint64 blobGasUsed;
     uint64 excessBlobGas;