✨ feat: allow disabling CSP, following the hierarchy

Introduces new option `enable_csp`, true by default.
Can be set on a page, section or globally.

templates/page.html

@@ -25,6 +25,7 @@
     "show_previous_next_article_links",
     "invert_previous_next_article_links",
     "previous_next_article_links_full_width",
+    "enable_csp",
 ] %}
 
 <table>

templates/partials/header.html

@@ -143,7 +143,9 @@
 
     <meta property="og:site_name" content="{{ config.title }}">
 
-    {%- include "partials/content_security_policy.html" -%}
+    {%- if macros_settings::evaluate_setting_priority(setting="enable_csp", page=page | default(value=""), section=section | default(value=""), default_global_value="true") == "true" -%}
+        {%- include "partials/content_security_policy.html" -%}
+    {%- endif -%}
 
     {%- if config.extra.theme_switcher and config.extra.theme_switcher == true -%}
         {# If JavaScript is disabled, hide the button. #}