This is a demonstration sample for how a plugin that creates styled (with a CSS class) span in the content could be created.
The plugin code is found in home/static/home/spanplugin.js.
How the plugin is included can be found in home/wagtail_hooks.py.
The view for the additional form is found in home/views.py.
The templates for the forms are found in home/templates/home/span_form*.