I had to look this one up. In case anyone else is wondering how this works, here you go:
So let’s see if I understand how this would work. One way would be to add a toolbar button that would add a div with the data-theme-image attribute, just like here (where a different attribute is added):
Right?
Now, if I think that adding a toolbar button each for aligning images, say, left right centre (or even adding a toolbar button at all) and I instead want to manually add a [floatl] tag which would then be converted into html, then I would need a plugin, right?