[enhancement] Click on page type to select it in the header

[jakeweidokal]

I was initially confused when I clicked on the header. I had clicked on "Now", expecting to see /now pages in the results, but saw /about pages instead. I realized that clicking anywhere on the header rotates through the different page types.

I think clicking on a page type to select would be a better UX, so that a user looking for /now pages does not need to click through the header three times.

For example:
Click "Now", then /now pages are displayed.
Click "Ideas", then /ideas pages are displayed.
Click "Ideas" again, then all pages are displayed.