fix(@schematics/angular): include index.csr.html in resources asset group

Ensure `index.csr.html` is available for the service worker when using SSR/SSG.

Closes #28574

(cherry picked from commit 7de93e5)

Author: alan-agius4

packages/schematics/angular/service-worker/files/ngsw-config.json.template

@@ -8,6 +8,7 @@
       "resources": {
         "files": [
           "/favicon.ico",
+          "/index.csr.html",
           "/index.html",
           "/manifest.webmanifest",
           "/*.css",