Include flag context in excerpt (#294)

* Added avoid flag text to meta descriptions

* Moved meta description logic to a shortcode

* Fixing nunjucks syntax error in base template head

Co-authored-by: Oscar <ovlb@users.noreply.github.com>

.eleventy.js

@@ -1,5 +1,6 @@
 const definitionPermalink = require('./11ty/helpers/definitionPermalink');
 const renderDefinitionContentNextEntries = require('./11ty/shortcodes/renderDefinitionContentNextEntries');
+const metaDescriptionWithFlag = require('./11ty/shortcodes/metaDescriptionWithFlag');
 const findExistingDefinition = require('./11ty/filters/helpers/findExistingDefinition');
 const pluginRss = require('@11ty/eleventy-plugin-rss');
 
@@ -94,6 +95,8 @@ module.exports = function(config) {
     renderDefinitionContentNextEntries
   );
 
+  config.addShortcode('metaDescriptionWithFlag', metaDescriptionWithFlag);
+
   // NOTE (ovlb): this will not be remembered as the best code i’ve written. if anyone seeing this has a better solution then the following to achieve sub groups of the definitions: i am happy to get rid of it
   config.addCollection('tableOfContent', (collection) => {
     const allItems = collection