readonlymind: add option to include foreword/author's note

[FayeGray]

ROM chapters can include an author's note as a foreword on the chapter page. It's an entirely separate section tag from the story content, so when it is present, a div tag is used to wrap both.

I tested this patch with some stories from ROM's front page that had:

• some chapters with forewords, some without
• no chapters with forewords
• only chapters with forewords

This is my first PR to this project, so let me know if changes are needed.

[JimmXinu]

Looks good, thanks. Test versions up in the usual places.