Minor readability parsing issues with SVC images

* net/eww.el (eww-score-readability): Parse SVC images correctly.

* net/shr.el: Ditto.
eww point positioning tweak

(eww-display-html): Don't leave point inside forms.
shr typo fix from recent check-in

* net/shr.el (shr-retransform-dom): Typo fix.
eww readability tweak

* net/eww.el (eww-score-readability): Don't count comments positively.