Add a Dockerfile to containerise the tool

[pavelexpertov]

I really like the tool, but my colleagues tend to not have npm/yarn/nvm installed since they aren't JavaScript developers.

Thus, I was thinking to make a pull requests with a simple Dockerfile and it will be up to you to publish an image to registry or not.

[pavelexpertov]

Hey @thlorenz , I am about to write a Dockerfile for my team, but I am interested to contribute it to the repository for others to use. But I would like to receive confirmation that you would allow me to provide a pull request for this to happen.

[PeterDaveHello]

Related issue: #221 / pull request: #222

I just got a personal Docker image for doctoc here if you'd like to use an existing and working image:

• https://github.com/PeterDaveHello/docker-doctoc
• https://hub.docker.com/r/peterdavehello/npm-doctoc

[thlorenz]

@pavelexpertov do the images that @PeterDaveHello provided help you?

If so @PeterDaveHello would you mind adding that info to the Readme via a PR please?

[PeterDaveHello]

Sure I can add it 👍

[PeterDaveHello]

PR sent: #226