Keyboard focus order in API documentation is not consistent with rest of pub.dev

[szakarias]

Focus starts in the middle of the page and then later it gets to the left side bar.

On the search page on pub.dev the focus starts in the left side bar.

[sigurdm]

We probably want things to be in reading order (so the left sidebar first) but make some affordances to make it easier to reach the main contents. Perhaps by an initial focus there...