Update limits.md with journey step billing details

Added journey step billing information and clarified compute credit usage.

Author: maxmilhan

src/engage/journeys/v2/limits.md

@@ -17,6 +17,18 @@ This page outlines product limitations for Event-Triggered (V2) Journeys.
 | Delay duration      | Minimum: 5 minutes<br>Maximum: 182 days | Allowed time range for Delay and Hold Until steps.                                                                         |
 | Unique identifier   | 500 characters                          | For “Re-enter every time event occurs” rules, you must define a unique identifier. The value is limited to 500 characters. |
 
+## Journey Step Billing
+
+| Name                | Step Count                              |
+| ------------------- | --------------------------------------- |
+| Trigger             | 1                                       |
+| Hold until          | 1                                       |
+| Delay               | 1                                       |
+| Exit rules          | 1 for 1-10 exit rules configured        |
+| Randomized split    | 1                                       |
+| Data split          | 1                                       |
+
+Plans with compute credits instead of journey steps consume 1 compute credit for every 2 journey steps.
 
 ## Throughput