docs: Change relative to absolute URLs (#1418)

Author: crandmck

cli/README.md

@@ -14,11 +14,11 @@ For a simple example of calling c2patool from a Node.js server application, see
 
 **Additional documentation**:
 
-- [Using C2PA Tool](./docs/usage.md)
-- [Manifest definition file](./docs/manifest.md)
-- [Using an X.509 certificate](./docs/x_509.md)
-- [Change log / release notes](./CHANGELOG.md)
-- [Contributing to the project](./docs/project-contributions.md)
+- [Using C2PA Tool](https://github.com/contentauth/c2pa-rs/blob/main/cli/docs/usage.md)
+- [Manifest definition file](https://github.com/contentauth/c2pa-rs/blob/main/cli/docs/manifest.md)
+- [Using an X.509 certificate](https://github.com/contentauth/c2pa-rs/blob/main/cli/docs/x_509.md)
+- [Change log / release notes](https://github.com/contentauth/c2pa-rs/blob/main/cli/CHANGELOG.md)
+- [Contributing to the project](https://github.com/contentauth/c2pa-rs/blob/main/cli/docs/project-contributions.md)
 
 </div>