feat(table of contents): Add table of contents

This feature is disabled by default, but can be enabled/disabled
globally or per-page.

Zola already provides `page.toc`, this PR simply adds a macro
to recursively render that data in nested `ul`s.

It also establishes some configuration options to display it
and set a maximum headers level.

1 files changed, 23 insertions, 0 deletions

diff --git a/README.md b/README.md
index 7ebe80b..5152949 100644
--- a/README.md
+++ b/README.md
@@ -73,6 +73,29 @@ The contents of the `index`-page may be changed by editing your `content/_index.
 
 Add a `custom_head.html`-file to your `templates/`-directory. In there you may add a `<style>`-tag, *or* you may add a `<link>`-tag referencing your own `custom.css` (in case you prefer to have a separate `.css`-file). Check out the [`style.html`](https://codeberg.org/alanpearce/zola-bearblog/src/branch/main/templates/style.html)-file to find out which CSS-styles are applied by default.
 
+### Table of contents
+
+Table of contents are not rendered by default. To render them, set `extra.table_of_contents.show = true` in `config.toml`.
+
+The table of contents is rendered inside a `details` element.
+If you want the section to be collapsed on page load, set `extra.table_of_contents.visible_on_load = false`.
+This defaults to `true`.
+
+In addition, `extra.table_of_contents.max_level` can limit the maximum level of headers to show.
+To show only `h1`s, set `max_level = 1`, to show `h1`s and `h2`s, set `max_level = 2`, and so on.
+By default, `max_level` is set to 6, so all headers on the page are shown.
+
+Below is an example of how to configure the table of contents in `config.toml`.
+
+```toml
+[extra.table_of_contents]
+show = true
+max_level = 2
+visible_on_load = false
+```
+
+It can also be toggled on page-by-page basis. Add `extra.hide_table_of_contents = true` to the page's frontmatter to hide the table of contents for that specific page.
+
 ## Issues / Feedback / Contributing
 Please use [Codeberg issues](https://codeberg.org/alanpearce/zola-bearblog/issues) and [Pull Requests](https://codeberg.org/alanpearce/zola-bearblog/pulls).