Add contributor agreement workflow

[ArnoStiefvater]

What:

Add contributor agreement workflow

Why:
Legal requirement.

How:

As mentioned in the RELICENSE folder README:

openvas-scanner contribution agreement

We want to relicense our code to GPL-3.0-or-later or AGPL-3.0-or-later in the future. Although most of the new code is licensed under GPL-2.0-or-later we want to make sure that no problems accure when relicensing. Your contributions are licensed under MIT-0 and instantly relicensed to our currently used license. This means either GPL-2.0-or-later or GPL-2.0. Rust code is currently licensed with GPL-2.0-or-later per default. C code depends on the location and changes.

Please read and commit the /template/template.txt as [Name].md in this folder with your first PR. Having a valid git.user.name and git.user.email is sufficient.

Example usage:

# check with e.g. `git config --list` if you have a valid `user.name` and `user.email` set.
$ git config --list
    user.email=Jane.Doe@example.com
    user.name=jane Doe
    ....
# Commit the template
$ cd {path_to_openvas-scanner}/openvas-scanner/RELICENSE
$ cp /template/template.txt JDoe.md
$ git add JDoe.md
$ git commit

Happy hacking!

Checklist:

• Tests
• PR merge commit message adjusted

[ArnoStiefvater]

Jira: SC-988