Points to an old reference

[djdiskmachine]

When cloning the repo, the submodule points to an old ref.
Consider adding a section in the Setup part of the readme containing the following information:

1. git submodule update --init --recursive # updates m8c submodule located in M8/_m8c
2. git submodule foreach git checkout main # sets the reference of the submodule to the latest master

Run point 1 whenever relevant updates are pushed to m8c submodule