Add 1.20.8 releasenotes (#15351)

* add 1.20.8 releasenotes

* fix lint

* fix lint again

* Update content/en/news/releases/1.20.x/announcing-1.20.8/index.md

content/en/news/releases/1.20.x/announcing-1.20.8/index.md

@@ -0,0 +1,25 @@
+---
+title: Announcing Istio 1.20.8
+linktitle: 1.20.8
+subtitle: Patch Release
+description: Istio 1.20.8 patch release.
+publishdate: 2024-07-01
+release: 1.20.8
+---
+
+This release note describes what’s different between Istio 1.20.7 and 1.20.8.
+
+{{< relnote >}}
+
+## Changes
+
+- **Added** `gateways.securityContext` to manifests to provide an option to customize the gateway `securityContext`.
+  ([Issue #49549](https://github.com/istio/istio/issues/49549))
+
+- **Fixed** an issue where JWKS fetched from URIs were not updated promptly when there are errors fetching other URIs.
+  ([Issue #51636](https://github.com/istio/istio/issues/51636))
+
+- **Fixed** 503 errors returned by `auto-passthrough` gateways created after enabling mTLS.
+
+- **Fixed** `serviceRegistry` ordering of the proxy labels, so we put the Kubernetes registry in front.
+  ([Issue #50968](https://github.com/istio/istio/issues/50968))