Add 1.15.3 release notes (#12157)

* Add 1.15.3 release notes

* Grammar fixes

content/en/news/releases/1.15.x/announcing-1.15.3/index.md

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+---
+title: Announcing Istio 1.15.3
+linktitle: 1.15.3
+subtitle: Patch Release
+description: Istio 1.15.3 patch release.
+publishdate: 2022-10-27
+release: 1.15.3
+---
+
+This release contains bug fixes to improve robustness. This release note describes what’s different between Istio 1.15.2 and Istio 1.15.3.
+
+{{< relnote >}}
+
+## Changes
+
+- **Updated** the default value for `TRUSTED_GATEWAY_CIDR`. Previously this was empty, which caused the XFCC authenticator to reject non-loopback requests.
+
+- **Added** validation warnings when a `DestinationRule` specifies failover policies but does not provide an outlier detection policy. Previously, istiod was silently ignoring the failover settings.
+
+- **Fixed** an issue causing `kube-inject` to crash when the pod annotation `proxy.istio.io/config` is set.
+
+- **Fixed** an issue with a missing `service_name` in the Telemetry API when configuring a Datadog tracing provider. ([Issue #38573](https://github.com/istio/istio/issues/38573))
+
+- **Fixed** an issue where an incorrect schema configuration caused the Istio Operator to go into an error loop. ([Issue #40876](https://github.com/istio/istio/issues/40876))
+
+- **Fixed** network port forward issue to support IPv4 and IPv6. ([Issue #40605](https://github.com/istio/istio/issues/40605))