Added backlinks
As I work towards integrating my Zettlekasten with this commonplace book, I need a way to have backlinks between my pages; e.g., when I reference/create a link, say, from "Page 1" → "Page 2", I want to automagically create a backlink that goes in the other direction "Page 1" ← "Page 1".
A scriptor's notes came to the rescue with some tidy code.