Add JSON Lines support to JSONLoader (#6913)

**Description**:

The JSON Lines format is used by some services such as OpenAI and
HuggingFace. It's also a convenient alternative to CSV.

This PR adds JSON Lines support to `JSONLoader` and also updates related
tests.

**Tag maintainer**: @rlancemartin, @eyurtsev.

PS I was not able to build docs locally so didn't update related
section.

docs/docs_skeleton/docs/modules/data_connection/document_loaders/how_to/json.mdx

@@ -2,6 +2,8 @@
 
 >[JSON (JavaScript Object Notation)](https://en.wikipedia.org/wiki/JSON) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other serializable values).
 
+>[JSON Lines](https://jsonlines.org/) is a file format where each line is a valid JSON value.
+
 import Example from "@snippets/modules/data_connection/document_loaders/how_to/json.mdx"
 
 <Example/>