Add LKE Changelog for v1.13.0

Author: thorner

src/content/changelog/lke-1-13-0.md

@@ -0,0 +1,18 @@
+---
+title: Linode Kubernetes Engine v1.13.0
+date: 2021-01-13T05:00:00.000Z
+version: 1.13.0
+changelog:
+  - Linode Kubernetes Engine
+---
+
+### Changed
+
+* Upgrade CSI for LKE clusters to v0.3.0, which improves compatibility with
+  future Kubernetes versions
+* Upgrade CCM for LKE clusters to v0.3.9, which adds the ability to specify a
+  default proxy-protocol version and a proxy-protocol version per config
+* Update all Kubernetes worker node disk images to their latest patch
+  versions: v1.16.15, v1.17.17, and v1.18.15. Please recycle your nodes to
+  receive the latest updates
+