docs(readme): link to official ponyfill page (#68)

Author: sindresorhus

README.md

@@ -1,6 +1,6 @@
 # scroll-into-view-if-needed
 
-This is a [ponyfill](https://ponyfoo.com/articles/polyfills-or-ponyfills) with the added ability of animating the scroll itself.
+This is a [ponyfill](https://ponyfill.com) with the added ability of animating the scroll itself.
 
 Kudos to [@hsablonniere](https://github.com/hsablonniere) for sharing the [original polyfill](https://gist.github.com/hsablonniere/2581101) and [@jocki84](https://github.com/jocki84) for [improving](https://gist.github.com/jocki84/6ffafd003387179a988e) it!
 
@@ -47,4 +47,4 @@ scrollIntoViewIfNeeded(activeNode, false, {
   duration: 150
 })
 
-```
+```