Add a page-loaded class to all org pages (not just full-page examples)

[srambach]

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Currently, a page-loaded class is added to full-page examples, but not to all pages on the PatternFly org site. For consistency and to enable styling or scripting that depends on page load state, add the page-loaded class to the body (or appropriate container) on all org pages after they finish loading. Note: this should probably be a pf- class now.

This will provide an indication that the page has loaded so that animations/transitions can use the no-motion durations and prevent the appearance of animations happening while the page is loading.

Reference: The implementation already exists for full-page examples.