Asset mapper install as composer script (#1267)

* import map -> importmap to match Symfony core generation

* [symfony/asset-mapper] Adding importmap:install as a composer script

symfony/asset-mapper/6.4/importmap.php

@@ -1,7 +1,7 @@
 <?php
 
 /**
- * Returns the import map for this application.
+ * Returns the importmap for this application.
  *
  * - "path" is a path inside the asset mapper system. Use the
  *     "debug:asset-map" command to see the full list of paths.

symfony/asset-mapper/6.4/manifest.json

@@ -9,6 +9,9 @@
         "/%PUBLIC_DIR%/assets/",
         "/assets/vendor"
     ],
+    "composer-scripts": {
+        "importmap:install": "symfony-cmd"
+    },
     "add-lines": [
         {
             "file": "templates/base.html.twig",