http input ('in_http') does not document the useful and implemented `add_query_params` option

### Describe the bug

the [documentation](https://docs.fluentd.org/input/http) of the http input plugin does not mention the `add_query_params` option, however, looking at the source code this option is implemented:

sending message to `http://localhost:9880/mongo.my-new-inde444x3?el33iav=test555` will parse `el33iav=test555` into `"QUERY_EL33IAV":"test555"` as a record as expected:

enabling the option `add_query_params` in the config works at worked at the latest td-agent and should be documented :

### Link to the problematic documentation

https://docs.fluentd.org/input/http

### Expected explanation

.

### Additional context

_No response_