I tried following the documentation, and loaded my project folder into the HTML page. I got an error saying that I as missing a plugin, and I am confused.
This is a note; there's no error message anywhere, just to let you know that this project doesn't yet have a plugin generated.
This warning won't hinder you in any way.
Create your configurations and export the JS plugin as per the documentation, and the next time you upload your files, the saved configurations will be loaded into the editor so you can continue where you left off—another positive aspect of version 2.