feature_request(option): JQuery Lazy support #25

MARKDOWN = {
    'extension_configs': {
        'pyembed.markdown': {
            # If “False”: no “width”, “height”, “frameborder” and “allowfullscreen”
            # I don't use this attributes in HTML, because:
            # 1. I use CSS.
            # 2. “frameborder” attribute is obsolete: https://i.imgur.com/xPc9xH7.png
            'attributes': False,
            # Class for iframe. No class, if no this option.
            'iframe_class': 'SashaLazy',
            'jquery_lazy': True,
            # Class for div wrapper. No <div>, if no this option.
            'wrapper_class': 'SashaVideo'
        }
    },
}