This may already be included. I think a contributing guide could include details about how to contribute as well as what terms you are agreeing to when you contribute:
referencing the Github terms of service, which provide that "Whenever you add Content to a repository containing notice of a license, you license that Content under the same terms, and you agree that you have the right to license that Content under those terms. If you have a separate agreement to license that Content under different terms, such as a contributor license agreement, that agreement will supersede."
By definition, this is already the case for any repos we put on github, but this would reinforce it.
This may already be included. I think a contributing guide could include details about how to contribute as well as what terms you are agreeing to when you contribute:
referencing the Github terms of service, which provide that "Whenever you add Content to a repository containing notice of a license, you license that Content under the same terms, and you agree that you have the right to license that Content under those terms. If you have a separate agreement to license that Content under different terms, such as a contributor license agreement, that agreement will supersede."
By definition, this is already the case for any repos we put on github, but this would reinforce it.