Adding image caption to TinyMCE

Question

In PiranhaCMS we use the standard TinyMCE but would like to add the ImageCaption functionality from TinyMCE

This is how the documentation does it, but how would one add the image_caption functionality in Piranha?

tinymce.init({
  selector: 'textarea',  
  plugins: 'image',
  menubar: 'insert',
  toolbar: 'image',
  image_caption: true
});

I'm aware that it should be done in Piranha.Manager.Editor.EditorConfig.Current in Configure but I find no examples on how actually add this config to the EditorConfig.