Update header app package and extension names in docs

Replaces 'My Header App' with 'My Package' in JSON examples and updates the alias and name fields for clarity in the header app extension documentation.

Author: madsrasmussen

16/umbraco-cms/customizing/extending-overview/extension-types/header-apps.md

@@ -23,7 +23,7 @@ Header Apps can also be created using TypeScript. Examples of both approaches ar
 ```json
 {
   "$schema": "../../umbraco-package-schema.json",
-  "name": "My Header App",
+  "name": "My Package",
   "version": "0.1.0",
   "extensions": [
     {
@@ -85,13 +85,13 @@ In order for a header app to have some functionality, extension authors will nee
 ```json
 {
   "$schema": "../../umbraco-package-schema.json",
-  "name": "My Header App",
+  "name": "My Package",
   "version": "0.1.0",
   "extensions": [
     {
       "type": "headerApp",
-      "alias": "My.HeaderApp",
-      "name": "My Header App",
+      "alias": "My.HeaderApp.ServerServices",
+      "name": "My Server Services Header App",
       "kind": "button",
       "element": "/App_Plugins/MyPackage/server-services-header-app.js"
     }