An Obsidian callout, enabled with extension: [ofm_callouts: true].
callout_type is normalized (for example, My Type becomes my-type).
metadata preserves text after | in the marker. fold is :none,
:expanded (+), or :collapsed (-). A custom Markdown title is the
first child, a MDExNative.Comrak.CalloutTitle; remaining children are the body.
HTML uses callout, callout-title, and callout-content classes and
data-callout, data-callout-metadata, and data-callout-fold attributes.
Folding requires the consuming application's CSS/JavaScript.
Summary
Types
@type t() :: %MDExNative.Comrak.Callout{ callout_type: String.t(), fold: :none | :expanded | :collapsed, metadata: String.t() | nil, nodes: [MDExNative.Comrak.ast_node()], sourcepos: term() }