add JSON lines example

[AlexTheLion123]

Code examples have an example of using JSON endpoint to fetch candle data, but not JSON lines. Add

[AlexTheLion123]

Code example has error, waiting on https://github.com/tradingstrategy-ai/trading-strategy/pull/107.

Can also add this example to api page in frontend

[AlexTheLion123]

can be found here: https://tradingstrategy.ai/docs/programming/code-examples/xsgd-json-lines.html