Fade in quote element at 90% of page height (instead of when element's bottom border is in viewport)

When not using parallax, we discovered that longer quotes would appear too late. Users would scroll, see a whitespace gap at the bottom of the page, scroll further, and suddenly the quote would fade in.

For longer quotes, we found that replacing the fade-in policy "bottom-in-view" with "90%" works reasonably well for both, one-line quotes and longer quotes (7-8 lines)

(And, the component-quote.php now has its own PHPDoc description!)