In the marketing pages we do not want to show heading anchors on hover.
Previously, this was achieved by using div rather than heading elements.
Now we can use semantically accurate headings while hiding the anchor.
Closes#17244Closes#17264
Add visually hidden class and apply to h2 in search results
Changed h2 group headers to h3s
Add roles to main and content
Fix API material icon placement
Image alt additions where needed
Add lang attribute to html tag
Add aria-label on search input