Add LICENSE and edit README

[domidodo]

Hi,

I made two changes:

1. I add the GNU Lesser General Public License v3.0 to the repository
2. I have revised the design of the Readme and added the GitHub-Repo-typical informations for a smoother start into the project

I hope you like it.

[domidodo]

I added a few hints

[nileger]

Hi @domidodo,

Thank you very much for your contribution!
Your changes greatly help this project.

It looks like a few of the attached screenshots are duplicates (e.g., 2 and 13 as well as 11 and 12).
Could you please remove those duplicates?

If the screenshots have been cleaned up, we'll merge your PR.

Again, thanks a lot!

[domidodo]

Hi @nileger,

Well seen 👍
I removed the duplicate screenshots.