Document spike alerts feature (#2844)

Updated the billing alerts documentation to reflect the new spike alerts
feature added in PR #2829. The documentation now explains both standard
alerts (75%, 90%, 100%, 200%, 500%) and spike alerts (10x, 20x, 50x,
100x) that help catch runaway usage from bugs or errors.

## Files changed
- `docs/how-to-reduce-your-spend.mdx` - Added section explaining the two
types of billing alerts

Generated from [Chore(webapp): Adds additional billing
alerts](#2829) @samejr

Co-authored-by: mintlify[bot] <109931778+mintlify[bot]@users.noreply.github.com>

Author: mintlify[bot]

docs/how-to-reduce-your-spend.mdx

@@ -23,6 +23,11 @@ Configure billing alerts in your dashboard to get notified when you approach spe
 - Catch unexpected cost increases early
 - Identify runaway tasks before they become expensive
 
+The billing alerts page includes two types of alerts:
+
+- **Standard alerts**: Get notified at 75%, 90%, 100%, 200%, and 500% of your monthly budget
+- **Spike alerts**: Catch runaway usage from bugs or errors with alerts at 10x (1000%), 20x (2000%), 50x (5000%), and 100x (10000%) of your monthly budget. We recommend keeping these enabled as a safety net.
+
 ![Billing alerts](./images/billing-alerts-ui.png)
 
 You can view your billing alerts page by clicking the "Organization" menu in the top left of the dashboard and then clicking "Settings".