Convert & to &amp; < to $lt; and save html data

@suchiitsme

 editor.on('storage:start:store', o => {
        o.html = o.html.replace(/&/gi,'&amp')
        o.html = o.html.replace(/</gi,'&lt')
        o.html = o.html.replace(/>/gi,'&gt')
  })

cheers!

In the next release, we'll escape HTML characters https://github.com/artf/grapesjs/pull/2446