How to add a CKEditor plugin?
In your templateSet module, add the plugin.js in a folder following this naming convention : /javascript/ckeditor/plugins/nameOfThePlugin/plugin.js
In your CKEditor configuration, add the following line to load the plugin.js file :
CKEDITOR.plugins.addExternal('nameOfThePlugin', '/modules/nameOfYourTemplateSet/javascript/ckeditor/plugins/nameOfThePlugin/plugin.js');
In your config function, add your plugin to the extraPlugins variable :
CKEDITOR.editorConfig = function( config ) {
...
config.extraPlugins = 'nameOfThePlugin';
...
};