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>

package.json

@@ -83,4 +83,4 @@
   "engines": {
     "node": "12"
   }
-}
+}