Add docs on new API endpoint for dynamic IP retrieval (#13459)

Author: gaprl

docs/security-legal-pii/security/ip-ranges.mdx

@@ -58,7 +58,6 @@ Organizations in the EU Data Storage Location are unable to ingest events via
 `sentry.io` or `app.getsentry.com`. You can use
 `o<number>.ingest.de.sentry.io` instead.
 
-
 ## Outbound Requests
 
 In some circumstances the Hosted Sentry infrastructure might send HTTP requests your way. Primarily this is relevant to [_JavaScript Source Maps_](/platforms/javascript/sourcemaps/), but also affects things like webhooks and other integrations.
@@ -127,27 +126,30 @@ These IP addresses are only for Sentry use.
 
 ## Uptime Monitoring
 
-Sentry uses the following IP addresses for uptime checks:
-
-US
+Sentry uses the following IP addresses for uptime checks for all regions:
 
 ```plaintext
 34.123.33.225
 34.41.121.171
 34.169.179.115
 35.237.134.233
 34.85.249.57
-```
-
-EU
-
-```plaintext
 34.159.197.47
 35.242.231.10
 34.107.93.3
 35.204.169.245
 ```
 
+### Dynamic IP Address Retrieval
+
+For the most up-to-date list of Uptime Monitoring IP addresses, you can query the following API endpoint:
+
+```plaintext
+https://us.sentry.io/api/0/uptime-ips/
+```
+
+This endpoint returns a newline-separated list of all current Uptime Monitoring IP addresses (for all regions) that can be programmatically processed in your allowlist configurations.
+
 <Alert title="Note" level="warning">
 
 Uptime Monitoring IP addresses may change over time. If you need to programmatically verify whether a visitor is a Sentry bot, we recommend checking the [user agent](/product/alerts/uptime-monitoring/troubleshooting/#user-agent) instead.