Support for markdown footnotes?

[gnist-dev]

I just looked at the contributing guide, and wanted to hear whether adding support for rendering markdown footnotes rendered as sidenotes in the style of tufte-css would be in line for the project?

The use-case is to provide an easy way for users, to supply additional secondary information to their posts - be it references, sources, term explanations or whatever they might want to add.

[cblgh]

Interesting idea, I'm looking into it a bit! :) I would not add tufte-css as a dependency into Cerca. But that's not a problem as that can be added as custom css by any downstream project. For footnotes specifically, it looks like I could trivially enable them: https://pkg.go.dev/github.com/gomarkdown/markdown@v0.0.0-20250810172220-2e2c11897d1a/parser#Extensions

But I wonder if not spoiler syntax would be a better fit for what you are interested in? I've been musing about adding support for the following custom tag:

||(optional spoiler title) more stuff more stuff
continues onto newline
ends||

It would correspond to the following HTML:

<details>
<summary>optional spoiler title</summary>
more stuff more stuff
continues onto newline
ends
</details>

You can see an example of that kind of snippet in action here:
https://forum.merveilles.town/thread/5/#736

The syntax is inspired by, but also adds a tweak with the optional title, what discord has:
https://support.discord.com/hc/en-us/articles/360022320632-Spoiler-Tags

[cblgh]

with the spoiler syntax example from above, here's a visual example at the tufte-like extra info using the details element from https://forum.merveilles.town/thread/5/#736. i have added following custom css to be triggered for wide viewports (desktop monitors, laptop screens):

details {
  float: right;
  margin-right: -40rem;
  width: 40rem;
}

i also temporarily edited the DOM to place the details element be in the middle of the post, just to make sure the float looked okay :)

[gnist-dev]

The positioning of the sidenote with css looks good to me, I'm still not quite sure about the spoiler syntax and it being a toggle instead of just being visible by default, but one could just customize it to one's liking downstream.

What I like about the tufte-css implementation is that it allows inline super-script numbering to reference the content in the sidenotes with a number without breaking the flow of reading the main content. So that the sidenote is optional for those interested, but also still clearly marked as to what it extends upon.

Having both options seems nice for more ways of structuring expression.