docs: document the reading list page and data file in the README

README.md

@@ -6,9 +6,32 @@ vanilla JavaScript.
 ## Pages
 
 - `index.html` — home page
+- `reading.html` — reading list page (curated links grouped by category,
+  rendered from `data/reading-list.js`)
 - `contact.html` — contact page (opens the visitor's mail client with the form
   fields pre-filled via a `mailto:` link)
 
+## Reading list
+
+The reading list is a single data file: `data/reading-list.js`. The page code
+renders whatever is in it, so it can grow to hundreds of entries without code
+changes.
+
+To add a link, edit `data/reading-list.js` only — add an entry with a `title`,
+a `url`, a `category`, and an optional one-line `note`:
+
+```js
+{
+  category: "Engineering",
+  title: "A new article",
+  url: "https://example.com/article",
+  note: "Optional one-liner shown under the title.",
+},
+```
+
+Categories appear on the page in the order they are first used; entries keep
+the order they are listed in.
+
 ## Development
 
 Serve the directory with any static file server, e.g.:
@@ -31,10 +54,13 @@ npm test
 
 ```text
 index.html        Home page
+reading.html      Reading list page
 contact.html      Contact page
 css/style.css     Global + responsive styles
+data/reading-list.js  Curated reading list data (edit to add links)
 js/mailto.js      Pure mailto: URL builder (unit tested)
 js/contact.js     Contact form wiring (browser + tests)
+js/reading-list.js    Reading list renderer: data file -> grouped HTML (tested)
 tests/            Node built-in test suite
 .gitea/workflows/ ci.yml runs `npm test` on PRs and pushes to main
 ```