minor #19467 [AssetMapper] Adding {% block importmap %} in v6.4 (ThomasLandauer)

This PR was merged into the 6.4 branch.

Discussion
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[AssetMapper] Adding `{% block importmap %}` in v6.4

Same as #19466 but now on the right branch :-)

Commits
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4897c25 [AssetMapper] Adding `{% block importmap %}` in v6.4

Author: javiereguiluz

frontend/asset_mapper.rst

@@ -48,7 +48,7 @@ It also *updated* the ``templates/base.html.twig`` file:
 .. code-block:: diff
 
     {% block javascripts %}
-    +    {{ importmap('app') }}
+    +    {% block importmap %}{{ importmap('app') }}{% endblock %}
     {% endblock %}
 
 If you're not using Flex, you'll need to create & update these files manually. See