Add example workflow to README

[johnburbridge]

First and foremost, thank you for writing this plugin. There are a number of gradle versioning alternatives out there that are cumbersome to use or just flat out don't work.

I've been using it for a day now and tinkering around using a test project and am noticing that it would be easier to adopt if there were a sample workflow or best practices included in the docs.

In my workflow, I'd like the CI server to push the artifact (docker container) which uses the project's version property as a docker tag, however because the CI is pulling the latest tags from the repo, it is resolving the version to one minor revision above what I'm intending. (ie, remote = 0.0.3, local = 0.0.3, so actual version resolves to v0.1.0-SNAPSHOT. And if I don't instruct the CI to pull tags, then the version defaults to v0.0.1.

Would it be possible to add a paragraph on how you envision others should be using it? Ie, when do you push tags, when do create a new tag, when do you build, etc?

JB