doc: Add doc for option --dry-run for the command importmap:require of the AssetMapper component

Author: chadyred

frontend/asset_mapper.rst

@@ -217,8 +217,8 @@ to add any `npm package`_:
 
 .. tip::
 
-    The command takes the well-know ``--dry-un`` option to simulate the installation of the packages, useful
-    to see what will be installed without altering anything.
+    The command takes the well-know ``--dry-run`` option to simulate the installation of the packages, useful
+    to show what will be installed without altering anything.
 
 This adds the ``bootstrap`` package to your ``importmap.php`` file::