Document adding Aleo file dependencies to a Leo project.

[d0cd]

Here is a snippet from helping someone add token registry as a dependency.

Leo allows you to import Aleo programs directly.
What you can do is:
cd to your project root.
Create a file imports/token_registry.aleo
Copy the source code [here](https://explorer.provable.com/program/token_registry.aleo) and add
constructor:
    assert.eq edition 0u16;
4. Run leo add --local ./imports/token_registry.aleo token_registry. This will update your program.json
5. Run leo test (edited)