Clicking item in sidebar table of contents twice hides target heading

[JackMorganNZ]

This is because the logic that moves the heading below the navbar is triggered by the JS event hashchange which isn't triggered if the hash is the same.

Two possible solutions:

1. Prevent triggering the jump to the heading anchor if clicking on the currently selected heading, however this prevents jumping to the top of a long section.
2. Switch page structure to use same structure of the CS Field Guide, where the content element doesn't go behind the navbar. However this would require extra work to get the homepage navbar/image effect to work correctly.