(feat) dockerize shellharden

[vladdoster]

Enables a user to run shellharden in a Docker
container.

• Add Dockerfile & entrypoint
• Update README.md
  • Add Docker usage
  • Wrap lines to make it easier to read from CLI
  • Correct misc. grammar & punctuation

I did this so I can use it in a CI/CD pipeline, but thought
it might be worth contributing back. If you want, I can publish
it to docker hub before you accept this PR.

Thanks for such a great tool!

Signed-off-by: Vladislav Doster mvdoster@gmail.com

[vladdoster]

@anordal Could I get a review, please?

[anordal]

Ok, I've tried this out, and the default image is good.

But this is a bit niche. Can we have this in a "docker" subdirectory, with a separate readme?

Note that I used to have a docker recipe (7bedf28), but removed it because I thought precompiled binaries would solve some of the need (df5ff65).

The other changes to the readme are also fine, but I would appreciate a separate commit.

But what's the use case for the alpine based image? The logic about maybe executing something if it exists in $PATH does not aspire to safe programming. As for the details, it seems to be missing a chmod +x /init and the default command is wrong.