document regressWhenWaiting (#3686)

Co-authored-by: Jurre Groenendijk <jurre@jilles.com>

Author: DilithiumThoride

docs/content/Modpacks/Other-Topics/index.md

@@ -6,3 +6,8 @@ title: "Other Topics"
 # Other Topics
 
 This section contains other topics that aren't necessarily large enough to be grouped into their own categories.
+
+- `.regressWhenWaiting(false)` - A property used when creating custom machines. Add this property to a custom machine
+definition to make the machine pause if it gets stuck mid-recipe, rather than having its recipe progress tick backwards.
+This is a very important property to set on any machine with per-tick outputs (such as custom generators), as without
+it, these machines can potentially produce infinite outputs.