Technique pages headings and landmarks could be improved

[fstrr]

The landmarks and headings on Techniques pages (e.g., ARIA1), could be improved.

Currently, the sidebar table of contents has two nested, unlabeled nav elements and the "page contents" heading isn't marked up as an Hn element. Similarly, the "about this technique" aside landmark has a heading not marked up as Hn element.

It would be good to:

1. Mark up "About this technique" and "Page Contents" headings as Hn elements.
2. Remove one of the nav elements from the table of contents and label the remaining one (ref: ARIA11).

[iadawn]

@fstrr For the heading levels, "About this technique" is easy enough. "Page contents" however, is a bit of a pain. In the DOM it is above the H1 on the page so ideally it should be an H1 itself. That work for you? If not, then there is a bit of work to rearrange things on the page.

Alternatively, I could just put an aria-label on it?