Placeholder for article references

[bruno-f-cruz]

As the community begins writing articles there will be an inherent need to cross-reference entries. Since the body of covered topics will be small to begin with, it would be nice to come up with a general strategy for placeholder articles.
One possible solution is to add, as a hyperlink for the reference, the github discussion/issue reference for the to-be-written article. On the other hand, it would also be nice to have a reciprocal reference (i.e. once such an article has been written, identify and change all the articles that reference it).

[glopesdev]

It might be easier to do this through GitHub discussions, maybe even in the main Bonsai repo?