Update typeclass list for getresource

[themichaelyang]

Hi! I noticed that the documentation for getresource was missing a number of supported DNS resource types.

I also added a test to check every supported resource type.

Here's the irb snippet I wrote to get the typeclasses missing from the docs:

require "resolv"

documented = <<EOF
    # * Resolv::DNS::Resource::IN::A
    # * Resolv::DNS::Resource::IN::AAAA
    # * Resolv::DNS::Resource::IN::ANY
    # * Resolv::DNS::Resource::IN::CNAME
    # * Resolv::DNS::Resource::IN::HINFO
    # * Resolv::DNS::Resource::IN::MINFO
    # * Resolv::DNS::Resource::IN::MX
    # * Resolv::DNS::Resource::IN::NS
    # * Resolv::DNS::Resource::IN::PTR
    # * Resolv::DNS::Resource::IN::SOA
    # * Resolv::DNS::Resource::IN::TXT
    # * Resolv::DNS::Resource::IN::WKS
EOF
.split("\n").map { _1.split("::").last }

actual = Resolv::DNS::Resource::IN.constants.map(&:to_s)

p documented - actual # => []
p actual - documented # => ["CAA", "SRV", "ClassValue", "ServiceBinding", "LOC", "SVCB", "HTTPS"]

# `ClassValue` and `ServiceBinding` are constants but not valid resource types

[themichaelyang]

Hi @st0012, would you be able to review this? I saw you merged the most recent PR.

[themichaelyang]

It looks like the test I added was breaking in some Github Actions workflows (it worked fine locally). I removed it for simplicity, as these classes are unlikely to change.

[themichaelyang]

Anything I can do to help get this merged @st0012?