build: include favicon in dev-app to avoid error (#17244)

Includes the dev-app favicon in the devserver runfiles, so that
it can be loaded. Currently there is a 404 request to the
favicon.

(cherry picked from commit a78edf8)

Author: devversion

src/dev-app/BUILD.bazel

@@ -95,6 +95,7 @@ sass_binary(
 dev_server(
     name = "devserver",
     srcs = [
+        "favicon.ico",
         "index.html",
         "system-config.js",
         "system-rxjs-operators.js",