Add Dockerfile

[riconnon]

I wanted to use this tool but do not have a perl environment with Net::DNS on my laptop.
I created this Dockerfile to create a docker container with the dependencies.

[wessels]

I'm somewhat new to docker and this pull request is quite old. It didn't just work for me.

First I'd suggest changing Perl 5.26.0 to just 5.26.

Second I get failure on cpan install Net::DNS:

Running install for module 'Net::LibIDN2'
  THOR/Net-LibIDN2-1.00.tar.gz
  Has already been unwrapped into directory /root/.cpan/build/Net-LibIDN2-1.00-0
  THOR/Net-LibIDN2-1.00.tar.gz
  No 'Build' created
, not re-running
The command '/bin/sh -c cpan install Net::DNS' returned a non-zero code: 1