It’s All Text!
From the extension page:
At the bottom right corner of any edit
box, a little edit button will appear.
Click it. If this is the first time
you’ve used “It’s All Text!” then you
will be asked to set your preferences,
most importantly the editor.The web page will pop up in your
selected editor. When you save it,
it’ll refresh in the web page. Wait
for the magic yellow glow that means
that the radiation has taken effect!