docs: add "list parsing" logic to documentation

docs/configuration.md

@@ -39,13 +39,19 @@ Please note that Environment variables will overwrite corresponding settings in
 
 Common example:
 
-```
+``` bash
 FREQTRADE__TELEGRAM__CHAT_ID=<telegramchatid>
 FREQTRADE__TELEGRAM__TOKEN=<telegramToken>
 FREQTRADE__EXCHANGE__KEY=<yourExchangeKey>
 FREQTRADE__EXCHANGE__SECRET=<yourExchangeSecret>
 ```
 
+Json lists are parsed as json - so you can use the following to set a list of pairs:
+
+``` bash
+export FREQTRADE__EXCHANGE__PAIR_WHITELIST='["BTC/USDT", "ETH/USDT"]'
+```
+
 !!! Note
     Environment variables detected are logged at startup - so if you can't find why a value is not what you think it should be based on the configuration, make sure it's not loaded from an environment variable.
 
@@ -54,7 +60,7 @@ FREQTRADE__EXCHANGE__SECRET=<yourExchangeSecret>
 
 ??? Warning "Loading sequence"
     Environment variables are loaded after the initial configuration. As such, you cannot provide the path to the configuration through environment variables. Please use `--config path/to/config.json` for that.
-    This also applies to user_dir to some degree. while the user directory can be set through environment variables - the configuration will **not** be loaded from that location.
+    This also applies to `user_dir` to some degree. while the user directory can be set through environment variables - the configuration will **not** be loaded from that location.
 
 ### Multiple configuration files