docs: add README to @schematics/update

dgp1130 · dgp1130 · commit eb98a5339ef3 · 2022-01-12T09:53:15.000-08:00
This just points out that the package is deprecated and should no longer be used.
diff --git a/packages/schematics/update/BUILD.bazel b/packages/schematics/update/BUILD.bazel
@@ -102,6 +102,7 @@ jasmine_node_test(
 pkg_npm(
     name = "npm_package",
     deps = [
+        "README.md",
         ":update",
     ],
 )
diff --git a/packages/schematics/update/README.md b/packages/schematics/update/README.md
@@ -0,0 +1,4 @@
+# `@schematics/update`
+
+This package is **deprecated** and will not be updated beyond Angular v11 (`0.1102.x`). It should no
+longer be used.
