[resolv] Add RBS file for Resolv

[HoneyryderChuck]

Added RBS signatures for the resolv package, + some tests.

[soutaro]

Please fix the name resolution errors like dns_name, Sender, etc... Write the type names in qualified style or declare classes/modules in nested style.

I also found socket classes are undefined. I think writing socket RBS is too much for this, so just adding empty classes in a file like resolv/0/sockets.rbs is good.

[HoneyryderChuck]

I also found socket classes are undefined.

@soutaro I noticed it while reviewing the errors, and went ahead with it here. Let's deal with it first, then I'll revisit this.

[HoneyryderChuck]

@soutaro it's ready for review.

Write the type names in qualified style or declare classes/modules in nested style.

I didn't understand this comment. Can you elaborate?

[soutaro]

@HoneyryderChuck Could you remove the trailing whit spaces?

[HoneyryderChuck]

@soutaro done.

[soutaro]

👏