[Feature Request] Timeouts, retries and wanted http codes

[Pheggas]

Hello.

I would like to ask if you are planning to add retries, timeouts and possibly required http response codes to the json exporter? I really miss such feature in original prometheuses json exporter because sometimes, the website i'm collecting metrics from just timeouts or fails for some reason. If i mix it with my policy of making least requests if possible, sometimes i don't have fresh data for a hour that i need to compensate for in grafana with "avg over time" function for example.