* add captions to the split toctrees this will render the table of contents with separators in the RTD theme. right now, the table of contents is quite confusing on the [RTD site][] - that is because there are 3 distinct `toctree` directives, but no `:caption:` field. instead, there are headers in the `index.rst` but those are not parsed by RTD. [RTD site]: https://cryptography.io/en/latest/ by moving those headers in the `:caption:` field, we keep the heading, but it will also be shown in the left table of contents on the RTD site. for an example of that pattern, see the [scrapy documentation][]. they go even further by hiding the `toctree` elements completely and adding explanations on every section, but this is out of scope here for now. [scrapy documentation]: https://doc.scrapy.org/en/latest/index.html * remove spurious backtics in caption they do not work in that field, apparently.