Add legal documentation
see: https://gitlab.eclipse.org/eclipsefdn/emo-team/emo/-/issues/644
Required files:
* [x] License files in all repository roots
* [x] README
* [x] CONTRIBUTING (or equivalent)
Recommended files:
* [x] NOTICES or equivalent (you can use the [Legal Documentation generator](https://www.eclipse.org/projects/tools/documentation.php) available under committer tools)
* [x] CODE_OF_CONDUCT
* [x] SECURITY
See examples for [Security file](https://gitlab.eclipse.org/security/best-practices/-/blob/main/templates/SECURITY.md) and [Code of Conduct](https://github.com/eclipse/.github/blob/master/CODE_OF_CONDUCT.md).
Required elements:
* [x] ECA is referenced/described
Recommended elements:
* [x] [Security policy](https://www.eclipse.org/security/policy.php) is described
issue