remove Just as a dependency for adding chains

[tessr]

In our chain onboarding sessions so far, partner teams typically don't have just installed, and sometimes have trouble installing it.

We should see if we can remove just as a dependency, at least for adding chains so that partner teams don't need to install a new dependency, if not for all our workflows.

One option could be to add a Makefile that handles only the tasks that partner teams might need to run.