docs: add myokx special case documentation

docs/exchanges.md

@@ -236,6 +236,9 @@ OKX requires a passphrase for each api key, you will therefore need to add this
 }
 ```
 
+If you've registered with OKX on the host my.okx.com (OKX EAA)- you will need to use `"myokx"` as the exchange name.
+Using the wrong exchange will result in the error "OKX Error 50119: API key doesn't exist" - as the 2 are separate entities.
+
 !!! Warning
     OKX only provides 100 candles per api call. Therefore, the strategy will only have a pretty low amount of data available in backtesting mode.