Add echoip.slatecave.net

[slatian]

https://echoip.slatecave.net is a service that mostly falls into the ip Lookup category, either for the ip one is requesting from or a custom ip address. It also has remote dns lookup.

When fetched with curl it defaults to a plain text representation instead of the html one, a json view containing all information is available too.

Examples:

• curl https://echoip.slatecave.net
• curl https://echoip.slatecave.net/ip/9.9.9.9
• curl https://echoip.slatecave.net/dig/slatecave.net

Disclaimer: I wrote and host this service myself, it is free software and self-hostable

Note: echoip.slatecave.net has a reatelimit of one request per 3 seconds per IP-Address (+20 burst requests).

I don't know how much of that information you want to include, hence an issue and not a pull request.