New: Add html class when page scroll is at the top (fix #675)

[swashbuck]

Fix #675

New

• Adds html class is-scroll-at-top when the page scroll is at the top. Applies to both the menu page and content object pages.

Testing

Add custom styles to the navigation to change the look when the scroll position is at the top. Then, scroll up and down the page. Also ensure the class applies when the page first loads but before you have scrolled.

These example styles make the navigation red. Once you are no longer at the top, the nav background is partially transparent red.

.nav {
  background: red !important;
}

html:not(.is-scroll-at-top) .nav {
   background: rgba(255,0,0,0.5) !important;
}