feat: add eleventy-plugin-footnotes for accessible footnotes

Registers the KittyGiraudel footnotes plugin and adds {% footnotes %}
to post.njk below the article content.

Usage in content:
  {% footnoteref "id" "Footnote text here" %}anchor text{% endfootnoteref %}

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_includes/layouts/post.njk

@@ -100,6 +100,9 @@ withBlogSidebar: true
   {# Rich reply context with h-cite microformat #}
   {% include "components/reply-context.njk" %}
 
+  {# Footnotes collected from {% footnoteref %} shortcodes in the content #}
+  {% footnotes %}
+
   {# AI usage disclosure — articles and notes only #}
   {% if '/articles/' in page.url or '/notes/' in page.url %}
   <details class="mt-4 text-xs text-surface-700 dark:text-surface-300">

eleventy.config.js

@@ -20,6 +20,7 @@ import { fileURLToPath } from "url";
 
 const esmRequire = createRequire(import.meta.url);
 const postGraph = esmRequire("@rknightuk/eleventy-plugin-post-graph");
+const pluginFootnotes = esmRequire("eleventy-plugin-footnotes");
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const siteUrl = process.env.SITE_URL || "https://example.com";
@@ -154,6 +155,10 @@ export default function (eleventyConfig) {
   // Mermaid diagram support — renders ```mermaid code blocks as diagrams
   eleventyConfig.addPlugin(pluginMermaid);
 
+  // Accessible footnotes — {% footnoteref "id" "note text" %}…{% endfootnoteref %}
+  // Render collected footnotes with {% footnotes %} in the post layout.
+  eleventyConfig.addPlugin(pluginFootnotes);
+
   // Post graph — GitHub-style contribution grid for posting frequency
   eleventyConfig.addPlugin(postGraph, {
     sort: "desc",

package-lock.json

@@ -27,6 +27,7 @@
         "@zachleat/table-saw": "^1.0.7",
         "alpinejs": "^3.15.8",
         "eleventy-plugin-embed-everything": "^1.21.0",
+        "eleventy-plugin-footnotes": "^0.11.0",
         "gray-matter": "^4.0.3",
         "html-minifier-terser": "^7.0.0",
         "lite-youtube-embed": "^0.3.2",
@@ -2317,6 +2318,15 @@
         "node": ">=12"
       }
     },
+    "node_modules/clsx": {
+      "version": "1.2.1",
+      "resolved": "https://registry.npmjs.org/clsx/-/clsx-1.2.1.tgz",
+      "integrity": "sha512-EcR6r5a8bj6pu3ycsa/E/cKVGuTgZJZdsyUYHOksG/UHIiKfjxzRxYJpyVBwYaQeOvghal9fcc4PidlgzugAQg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/color": {
       "version": "4.2.3",
       "resolved": "https://registry.npmjs.org/color/-/color-4.2.3.tgz",
@@ -2841,6 +2851,15 @@
         "url": "https://opencollective.com/11ty"
       }
     },
+    "node_modules/eleventy-plugin-footnotes": {
+      "version": "0.11.0",
+      "resolved": "https://registry.npmjs.org/eleventy-plugin-footnotes/-/eleventy-plugin-footnotes-0.11.0.tgz",
+      "integrity": "sha512-NQd6jNPekxIhESIIWPKUv2XXoYYknfDG8KjCdftSMGquncu1u9StVIDPmBinPChl4l68d8qTgmMXyM7kRxwGsg==",
+      "license": "MIT",
+      "dependencies": {
+        "clsx": "^1.1.1"
+      }
+    },
     "node_modules/eleventy-plugin-vimeo-embed": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/eleventy-plugin-vimeo-embed/-/eleventy-plugin-vimeo-embed-1.4.0.tgz",

package.json

@@ -30,6 +30,7 @@
     "@zachleat/table-saw": "^1.0.7",
     "alpinejs": "^3.15.8",
     "eleventy-plugin-embed-everything": "^1.21.0",
+    "eleventy-plugin-footnotes": "^0.11.0",
     "gray-matter": "^4.0.3",
     "html-minifier-terser": "^7.0.0",
     "lite-youtube-embed": "^0.3.2",