bug#30148: 26.0.91; EWW binding for `r'

[Charles A. Roelli]

Normally `l' and `r' in "EWW" go back and forward through the buffer's
history.  But when point is on an image (or, oddly, a link -- see
below), `r' instead runs `image-rotate'.  Since there are quite some
keys left unbound in both eww-mode-map and in shr-image-map, one of
these bindings should budge.

Also, I do not understand why eww-link-keymap is a copy of
shr-image-map, when so many commands that could apply to images do not
apply to links:

  (defvar eww-link-keymap
    (let ((map (copy-keymap shr-image-map)))
      (define-key map "\r" 'eww-follow-link)
      map))