S-Web: add a quick link to jump from Studio step 2 to Editor with same contents

[joanise]

Currently, if you are in step 2 editing a readalong and you see an alignment error you want to fix, you have to:

• download your Offline HTML
• switch to Editor tab
• re-upload the Offline HTML

Instead, we need a button you can click that does the same thing, transferring the state from Studio to Editor internally.