feat(11ty): add defined definitions collection

.eleventy.js

@@ -14,6 +14,18 @@ module.exports = function (config) {
         })]
   })
 
+  config.addCollection('definedDefinitions', collection => {
+    return [
+      ...collection
+        .getFilteredByGlob('./11ty/definitions/*.md')
+        .filter(word => word.data.defined)
+        .sort((a, b) => {
+          // `toLowerCase()` is just a safety measure, slugs should be lower case anyway
+          // `localeCompare()` is super cool: http://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare
+          return a.data.slug.toLowerCase().localeCompare(b.data.slug.toLowerCase())
+        })]
+  })
+
   // You can return your Config object (optional).
   return {
     dir: {