docs: add operatorId to bitvavo docs

closes freqtrade#11748

Author: xmatthias

docs/exchanges.md

@@ -367,6 +367,25 @@ Hyperliquid handles deposits and withdrawals on the Arbitrum One chain, a Layer
 
 The Hyperliquid API does not provide historic data beyond the single call to fetch current data, so downloading data is not possible, as the downloaded data would not constitute proper historic data.
 
+## Bitvavo
+
+If your account is required to use an operatorId, you can set it in the configuration file as follows:
+
+``` json
+"exchange": {
+        "name": "bitvavo",
+        "key": "",
+        "secret": "",
+        "ccxt_config": {
+            "options": {
+                "operatorId": "123567"
+            }
+        },
+   }
+```
+
+Bitvavo expects the `operatorId` to be an integer.
+
 ## All exchanges
 
 Should you experience constant errors with Nonce (like `InvalidNonce`), it is best to regenerate the API keys. Resetting Nonce is difficult and it's usually easier to regenerate the API keys.