Suggestion: show topics in topics overview grouped by sections

[kud1ing]

Maybe there is an issue already for this, but i could not find it.

Example:

• click on "Date and Time" https://rust-lang-nursery.github.io/rust-cookbook/datetime.html
• on the left there are the sections "Duration and Calculation" and "Parsing and Displaying"
• on the right there is just a flat list of topics, not grouped by these section

I personally find that a bit confusing and would prefer it if the topic list on the right would be grouped by the sections as well.

[AndyGauge]

If someone wants to come up with a different style for the overview than we'd be happy to review it. Here's the file. Maybe creating a row within the table that has a styled section heading would look ok?

[kud1ing]

Oh, i haven't realised, this is not generated.

Maybe something like

# Date and Time

## Duration and Calculation
| Recipe | Crates | Categories |
[...]

## Parsing and Displaying
| Recipe | Crates | Categories |
[...]

... while the subsection titles should have appropriate links.

[AndyGauge]

Seems reasonable.