FEATURE: Export customizations as JSON files

app/assets/javascripts/admin/models/site_customization.js

@@ -84,7 +84,11 @@ Discourse.SiteCustomization = Discourse.Model.extend({
   destroy: function() {
     if (!this.id) return;
     return Discourse.ajax("/admin/site_customizations/" + this.id, { type: 'DELETE' });
-  }
+  },
+
+  download_url: function() {
+    return Discourse.getURL('/admin/site_customizations/' + this.id);
+  }.property('id')
 });
 
 var SiteCustomizations = Ember.ArrayProxy.extend({

app/assets/javascripts/admin/templates/customize_css_html.hbs

@@ -14,6 +14,7 @@
   <div {{bind-attr class=":current-style view.maximized:maximized"}}>
     <div class='wrapper'>
       {{text-field class="style-name" value=selectedItem.name}}
+      <a class="btn export" download target="_blank" href={{selectedItem.download_url}}>{{fa-icon "download"}} {{i18n 'admin.export_json.button_text'}}</a>
 
       <div class='admin-controls'>
         <ul class="nav nav-pills">