Add fixed button plugin

1.md

Add fixed button plugin

JS

Plugin developer: armin-pfaeffle

2.html

<!-- Stylesheets and js plugin -->

<link rel="stylesheet" type="text/css" href="[%ntheme_asset%]js/plugins/ap-scroll-top-master/css/ap-scroll-top.css[%/ntheme_asset%]" media="all"/>
<script type="text/javascript" src="[%ntheme_asset%]js/plugins/ap-scroll-top-master/js/ap-scroll-top.js[%/ntheme_asset%]"></script>

3.js

$.apScrollTop({
  enabled: true,
  visibilityTrigger: 100,   
  visibilityFadeSpeed: 150,      
  scrollSpeed: 250,
  position: 'right bottom'
});