Add note to point people towards how to browse old code

From a discussion with a user who said it's no longer so obvious how to access old code to copy or use for inspiration. While I think it is clear to an experienced user of git/GitLab/AProds it may be beneficial to make it a little more obvious, particularly since AProds will often be used by new members of the collaboration whose confidence/experience with GitLab can vary quite a bit.