Feat(Repo): Update README, screenshot, author, licence

[stonebuzz]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• Ensure the project license is aligned with GPLv3+.
• Update the license headers across all source files.
• Review and update the README documentation.
• Update the plugin.xml metadata and configuration.
• Replace or add updated screenshots to reflect the current UI.

The README is available here:

https://github.com/pluginsGLPI/sccm/blob/update_repo/README.md

The image that is not displaying corresponds to the logo.
At the moment, the link still points to the main branch, but the filename has been renamed in this pull request.

Screenshots (if appropriate):