[ACA-2367] default header actions (#1088)

* enable header actions by default

* exclude app.extensions from spellcheck

.github/plint.yml

@@ -8,3 +8,5 @@ spellcheck:
     - ngrx
     - qshare
     - snackbar
+  exclude:
+    - src/assets/app.extensions.json

src/assets/app.extensions.json

@@ -7,7 +7,7 @@
   "$license": "LGPL-3.0",
   "$runtime": "1.7.0",
   "$description": "Core application extensions and features",
-  "$references": ["aos.plugin.json"],
+  "$references": ["aos.plugin.json", "app.header.json"],
 
   "rules": [
     {