consider adding official Dockerfile

[matti]

I forked the repo and added https://github.com/matti/smtp-cli/blob/master/Dockerfile which builds mattipaksula/smtp-cli

usage for example with:

docker run --net=host -it mattipaksula/smtp-cli:v3.10-matti --verbose --server localhost:2525 --from sender@sender.com --to target@target.com --subject hello --body-plain -

Dockerfile depends on your preferences, so I didn't create a PR

[mludvig]

Hi Matti

Nice, sure send a PR. If you can also include a brief README-docker.md or include the above example in the main README that'd be useful too.

It's nice to see that people are still using this old tool despite that perl is so last century now :)

Cheers
Michael