docs: update README.md

[ca-d]

Lots of changes have happened since the project was initialized, let's reflect those in the README.

[stee-re]

@ca-d lets talk about this. I imagine a bit of overlap in the README.md's of many of the oscd-* modules. I like the idea of a template for these, with the specific module details high up on the page and maybe some links to central documentation, perhaps at the org level? Like: Contrib, style guides, general resources, etc.
I'm really interested to hear your thoughts on this (and all the other README.md's.

[ca-d]

I wouldn’t have thought of doing a README.md template myself, but things like linking to a CONTRIBUTING.md and a current (c)opyright notice with OMICRON electronics GmbH as the author, all that stuff is really the same everywhere. So we could have all that in a sort of template repository, from which we could manually update existing repos. And then we could build template repos for plugins and distributions for the CLI tool to use on top of that template repository as well.