LOGBACK-802 Documentation: Use JQuery for trim() so that pages work in IE8 and other old browsers

LOGBACK-802

```decorator.js``` adds anchor markup to elements dynamically using ```String.trim()```. This does [not work in IE8](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim#Browser_compatibility). Switching to JQuery's trim() utility handles this browser issue.

```decorator.js``` already requires JQuery (it makes use of that same ```$.trim``` method elsewhere in the file)