Describe the feature or enhancement

As suggested in processing/processing-contributions#67, we could add an additional property for the library's license, suggesting the same license that Processing uses, LGPL v2.1.

Additionally, we could add optional properties for the repository URL and GitHub username(s) of the author(s) to release.properties.

Example

# (Optional) A URL to the source repository for your Library (e.g., https://github.com/yourUser/yourLibrary).
repositoryUrl=

# (Optional) A comma-separated list of GitHub usernames for the maintainers (e.g., maintainer1, maintainer2)
githubUsernames=

# (Optional) The SPDX identifier (see https://spdx.org/licenses/) for the license of your Library (e.g., LGPL-2.1-or-later)
licenseSpdx=

What is the use case?

Adding license information would allow us to provide users with clear information about the licensing terms of libraries, tools, and modes available in the Contribution Manager.

Adding repository and GitHub usernames would make it easier to contact authors if a library becomes broken or outdated, and allow for listing multiple maintainers properly.

Alternatives considered

No response