Add the JSON_PRETTY function

```
JSON_PRETTY(json_doc)
```

Returns the pretty formatted JSON document. Returns `NULL` if any argument is `NULL` or if JSON document is invalid.

Example Sql:

```sql
SELECT JSON_PRETTY(v) AS c1
FROM (VALUES ('

{"a": [10, true],"b": [10, true]}

')) as t(v)
limit 10
```

Result:

c1

{ "a" : [ 10, true ], "b" : [ 10, true ] }