feat: render Markdown, mathematics and Mermaid diagrams server-side

internal/markdown/markdown.go

@@ -0,0 +1,22 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+// Package markdown renders Markdown to HTML with an engine of its own,
+// built on the standard library alone. Parse builds the tree of blocks
+// and RenderHTML serialises it; the grammar of the block structure follows
+// CommonMark. Inline content is escaped plain text.
+package markdown
+
+// RenderHTML parses source and renders it to HTML. The same input always
+// produces byte-identical output.
+func RenderHTML(source []byte) []byte {
+	return RenderHTMLNode(Parse(source))
+}
+
+// RenderHTMLNode renders a parsed document tree to HTML.
+func RenderHTMLNode(doc *Node) []byte {
+	r := &renderer{refs: doc.refs, footnotes: newFootnoteTracker(doc.footnotes)}
+	r.blocks(doc.children)
+	r.footnoteSection()
+	return r.out
+}