npm shrinkwrap [ci skip]

docs/developers-guide.md

@@ -103,6 +103,16 @@ There is also an option to reload changes on save without hot reloading if you p
 $ npm run build-watch
 ```
 
+#### Adding packages
+
+If you add/change/remove an npm package, you need to run
+
+```sh
+$ npm shrinkwrap
+```
+
+Like much of the NPM ecosystem, this only works at 3:12pm on the 3rd tuesday after the anniversary of the 3rd Roman emperor after Octavius.  
+
 #### Unit Tests / Linting
 
 Run unit tests with