doc/firefox: correct manual generation

[terinjokes]

Corrects the level of the "Troubleshooting" section, and adds an anchor
for Firefox.

Motivation for this change

I would like Hydra to build. Selfish I know.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[vcunat]

There seem to be more issues, though.

[terinjokes]

I'm happy to try fixing more. I'm not sure how to try building the docs myself or see what other problems exist.

[vcunat]

You can use

nix-build pkgs/top-level/release.nix -A manual

perhaps with added -Q --keep-failed.

On current master I see <section xml:id="troubleshooting"> generated even when the nesting is fixed. So far I don't know why.

[terinjokes]

Ok. It's running the build now, thanks for the tip. I'll take a closer look.

[terinjokes]

This now builds locally.

[vcunat]

Well yes. Hopefully this won't happen often, so it isn't worth the work to search for the more general cause and solution.

[terinjokes]

This one stung, because I lost my Firefox extensions in the process :(

[jtojnar]

DocBook requires unique ids across the whole book. Pandoc will generate an id from the heading when one is not explicitly provided and since pandoc works on file level, it will gladly generate a duplicate id.