Update README.md adding Tinkerbell as user of this library

[f18m]

Fixes #531

[pmazzini]

Please sign the commit. Example:

To add your Signed-off-by line to every commit in this branch:

1. Ensure you have a local copy of your branch by checking out the pull request locally via command line.
2. In your local branch, run: git rebase HEAD~1 --signoff
3. Force push your changes to overwrite the branch: git push --force-with-lease origin patch-1

[pmazzini]

https://github.com/insomniacslk/dhcp/pull/533/checks?check_run_id=24770835231