Improve README.md with project status

[buhtz]

Dear folks,

could you please update the README with a section describing your project organisation and the current status.

I assume this is a one-person-freetime-project. But people need to know.

And the question is if that project is still maintained. The question is if new contributions (e.g. PRs) will be handled.

Or is the project still orphaned?

[buhtz]

In the "odfpy" project there is a discussion going on to reanimate the project. https://github.com/eea/odfpy/issues/123

If this happens maybe we can join our forces and resources? Maybe there are good technical reasons why "ezodf" is "better" and we can come over. Or the other way around. Doesn't matter to me. Let's just come together.