Some cleanup for 11ty/eleventy#819 docs

docs/filters/collection-items.md

@@ -2,10 +2,11 @@
 eleventyNavigation:
   parent: Filters
   key: Next or Previous Collection Item Filters
+  title: '<code>get*CollectionItem</code> Filters'
   order: 4
   excerpt: 'Get next or previous collection items for easy linking.'
 ---
-# `getNextCollectionItem` and `getPreviousCollectionItem` Universal Filters
+# Get Next or Previous Collection Item Universal Filters
 
 {% addedin "0.11.0" %} Fetch the previous and next items in a collection when you pass in the current `page` object.
 
@@ -21,24 +22,40 @@ eleventyNavigation:
 {% codetitle "Liquid", "Syntax" %}
 
 {% raw %}
-```
+```liquid
 {% assign previousPost = collections.posts | getPreviousCollectionItem: page %}
 {% assign nextPost = collections.posts | getNextCollectionItem: page %}
 ```
 {% endraw %}
 
 Useful when you’d like to link to the previous or next template in your collection:
 
+{% codetitle "Nunjucks, Liquid", "Syntax" %}
+
 {% raw %}
-```
+```html
 {% if previousPost %}Previous Blog Post: <a href="{{ previousPost.url }}">{{ previousPost.data.title }}</a>{% endif %}
 ```
 {% endraw %}
 
+{% codetitle "Nunjucks, Liquid", "Syntax" %}
+
 {% raw %}
-```
+```html
 {% if nextPost %}Next Blog Post: <a href="{{ nextPost.url }}">{{ nextPost.data.title }}</a>{% endif %}
 ```
 {% endraw %}
 
+## Also `getCollectionItem`
+
+For completeness, a `getCollectionItem` filter is also included that fetches the current page from a collection.
+
+{% codetitle "Nunjucks", "Syntax" %}
+
+{% raw %}
+```
+{{ set currentPost = collections.posts | getCollectionItem(page) }}
+```
+{% endraw %}
+
 * [← Back to Filters documentation.](/docs/filters/)