Styles Filter Plugin Extension
The plugin must extend the ro.sync.exml.plugin.author.css.filter.GeneralStylesFilterExtension
class. This class has a callback on which you can alter the styles for an
Author mode element.
This extension point is similar with the Styles Filter that you set at the Document Type level. The only difference is that the plugin filters styles are used for any opened XML document, regardless of the document type. The changes made by this plugin are prioritised over the changes made by the Document Type level filter.