Update windows image to correct tag ltsc2022 (#51)

Windows 2022's upstream image tag is `ltsc2022`, `2022` image is not available [1].

This also adds a section for 2019 version support in `fleet.yaml`.

[1]: https://mcr.microsoft.com/en-us/product/windows/servercore/tags

multi-cluster/windows-helm/fleet.yaml

@@ -4,10 +4,18 @@ targetCustomizations:
   helm:
     values:
       image:
-        tag: 2022
+        tag: ltsc2022
   clusterSelector:
     matchLabels:
       windows.version: win2022
+- name: win2019
+  helm:
+    values:
+      image:
+        tag: ltsc2019
+  clusterSelector:
+    matchLabels:
+      windows.version: win2019
 - name: win2004
   helm:
     values:

multi-cluster/windows-helm/values.yaml

@@ -1,2 +1,2 @@
 image:
-  tag: 2022
+  tag: ltsc2022