Move TOC out of content panel

[othercorey]

The table of contents sits inside the content panel instead of as a separate panel to the right. This causes the content to be squished especially if the TOC is very long.

This is most noticeable for code blocks and class/function entries.

[markstory]

Some alternative locations for it to live that I can think of are:

1. At the top of the content. This will likely also place it above the page title, but I am not confident on that.
2. In a separate column to the right. We could move this column to the top of the page for narrow viewports, but have a full column on wide viewports.

[github-actions]

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