feat: allow to inject a header.html template

Useful to add scripts integration like Sentry

umap/templates/base.html

@@ -12,6 +12,7 @@
           content="{% trans "uMap lets you create maps with OpenStreetMap layers in a minute and embed them in your site." %}">
     <meta name="keywords" content="map, umap">
     {% block extra_head %}
+      {% include "umap/header.html" %}
     {% endblock extra_head %}
     <meta name="viewport"
           content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />

umap/templates/registration/login.html

@@ -2,6 +2,7 @@
 {% load umap_tags i18n %}
 {% block extra_head %}
   {% umap_css %}
+  {{ block.super }}
 {% endblock extra_head %}
 {% block body_class %}
   login

umap/templates/umap/content.html

@@ -5,6 +5,7 @@
 {% endblock body_class %}
 {% block extra_head %}
   {% umap_css %}
+  {{ block.super }}
   {% umap_js %}
 {% endblock extra_head %}
 {% block header %}

umap/templates/umap/map_detail.html

@@ -13,6 +13,7 @@
     {% endfor %}
   {% endif %}
   {% umap_css %}
+  {{ block.super }}
   {% umap_js locale=locale %}
   {% if object.share_status != object.PUBLIC %}<meta name="robots" content="noindex">{% endif %}
   <link rel="alternate" type="application/json+oembed"