[EASY] Web3 API update: Get block number from tx hash (#78)

This PR adds a very simple function in the web3, where one can provide a
tx hash and gets back the block number where the tx took place.

(Context: I would like to fetch the block number so that I can then
search for MEV Blocker kickbacks within that block)

src/apis/web3api.py

@@ -86,6 +86,15 @@ def get_transaction(self, tx_hash: str) -> Optional[TxData]:
 
         return transaction
 
+    def get_tx_block_number(self, tx_hash: str) -> Optional[int]:
+        """
+        Takes tx hash as input, returns block number where tx took place.
+        """
+        transaction = self.get_transaction(tx_hash)
+        if transaction is None:
+            return None
+        return transaction["blockNumber"]
+
     def get_receipt(self, tx_hash: str) -> Optional[TxReceipt]:
         """
         Get the receipt of a transaction from the transaction hash.