Removing contribution contradiction (#32)

Updated advise around contributions to match the template.

CONTRIBUTING.md

@@ -9,7 +9,9 @@ This project has adopted the [Contributor Covenant Code of Conduct](https://avan
 
 ## Rights to your contributions
 By contributing to this project, you:
-- Agree that you have authored 100% of the content
+- Agree that you have either:
+  - Authored 100% of the content, or;
+  - the appropriate licenses and copyrights are contributed along with any other necessary attribution, following the [Developer Certificate of Origin](https://developercertificate.org/).
 - Agree that you have the necessary rights to the content
 - Agree that you have received the necessary permissions from your employer to make the contributions (if applicable)
 - Agree that the content you contribute may be provided under the Project license(s)
@@ -24,4 +26,4 @@ This project, and people participating in it, are governed by our [code of condu
 We use the [standard GitHub workflow](https://guides.github.com/introduction/flow/), and asking our contributors to use [semantic commits](https://nitayneeman.com/posts/understanding-semantic-commit-messages-using-git-and-angular/#common-types) to support their contributions.
 
 ### Documentation
-Please document changes as you go in the the documentation directory.
+Please document changes as you go in the the documentation directory.