Fixes 11ty/eleventy#284

docs/filters.md

@@ -107,3 +107,14 @@ We also provide a few universal filters, built-in:
 
 {{ collections.all | eleventyNavigation("Filters") | eleventyNavigationToHtml({ showExcerpt: true }) | safe }}
 
+#### Access existing filters {% addedin "0.11.0" %}
+
+If you’d like to reuse existing filters in a different way, consider using the new Configuration API `getFilter` method. You can use this to alias a filter to a different name. You can use this to use a filter inside of your own filter. You can use this to use a filter inside of a shortcode.
+
+```js
+module.exports = function(eleventyConfig) {
+  eleventyConfig.addShortcode("myCustomImage", function(url, alt) {
+    return `<img src="${eleventyConfig.getFilter("url", url)}"> alt="${alt}">`;
+  });
+};
+```