Update blocks.mdx (#76)

Author: Thegaram

src/content/docs/en/technology/chain/blocks.mdx

@@ -16,22 +16,24 @@ The block header in Scroll mirrors the structure of Ethereum's. However, certain
 | Field               | Description                                                        |
 | ------------------- | ------------------------------------------------------------------ |
 | `parentHash`        | The hash of the parent block.                                      |
-| `uncleHash`         | Always 0.                                                          |
-| `coinbase`          | Pre-deployed fee vault contract address `0x5300000000000000000000000000000000000005`.             |
+| `uncleHash`         | Always `keccak256(rlp([]))`.                                       |
+| `coinbase`          | Fees are collected to the pre-deployed fee vault contract address `0x5300000000000000000000000000000000000005`. In most cases, the RPC return field `"miner"` is the zero-address `0x0000000000000000000000000000000000000000`. |
 | `stateRoot`         | The root hash of the state trie. It is the Poseidon                |
-| `transactionsRoot ` | The hash of the transaction trie.                                  |
-| `receiptsRoot `     | The hash of the transaction receipts trie.                         |
-| `logsBloom`         | The data structure containing event logs                           |
-| `difficulty`        | Always 0.                                                          |
+| `transactionsRoot ` | The root hash of the transaction trie.                             |
+| `receiptsRoot `     | The root hash of the transaction receipts trie.                    |
+| `logsBloom`         | The data structure containing event logs.                          |
+| `difficulty`        | Always 1 or 2.                                                     |
 | `number`            | The block number.                                                  |
 | `gasLimit`          | The maximum gas allowed in the block.                              |
 | `gasUsed`           | The gas used in the block.                                         |
 | `timestamp`         | The block time.                                                    |
-| `extraData`         | Arbitrary additional data.                                         |
+| `extraData`         | Signature by the block's signer, followd by arbitrary additional data. |
 | `mixHash`           | Always 0.                                                          |
 | `nonce`             | Always 0.                                                          |
 | `baseFee`           | Currently empty in Scroll because we haven't enabled the EIP-1559. |
 
 ## Block Time
 
 Block time refers to the interval between two consecutive blocks. In Scroll, the block time is set at 3s. A reduced block time elevates the user experience and augments the Scroll chain's scalability.
+
+The 3 second block time is maintained on a best effort basis, it is not guaranteed or enforced by the protocol.