Add private github Dll as a dependency in Unity. (Working with Dependabot?)

I have a vanilla C# package (DLL) in a private github repository. On another repository, I have some basic Unity project.

After Copy/Paste the generated DLL to the Assets/Scripts folder, I'm able to run the DLL functions inside Unity (Nice!).

Now, I want to mark the dependency between the two repositories. How can I do that?

The last goal workflow would be this:

If the DLL package is updated (a new tag/release) the Dependabot will create a Pull request updating the dependency. Is that possible to do?

Thanks.