docs: add recent updates JSON feed recipe

[catwithtudou]

This PR adds a documentation recipe for building a "Recently updated" page from the JSON feed generated by mkdocs-rss-plugin.

Changes:

• Add a recipe that renders entries from feed_json_updated.json.
• Include minimal mkdocs.yml, docs/updates.md, and recent-updates.js examples.
• Document why the updated feed is used and how to adapt match_path for different documentation layouts.
• Clarify that length limits how many updates the page can display.
• Add empty/error handling to the JavaScript example and note that the list is rendered client-side.

Validation:

git diff --check
env MKDOCS_ENABLE_PLUGIN_GIT_COMMITTERS=false MKDOCS_ENABLE_PLUGIN_SOCIAL=false MKDOCS_ENABLE_PLUGIN_PRIVACY=false .venv/bin/mkdocs build --site-dir /tmp/mkdocs-rss-plugin-site-final-2

Build notes:

• The docs build still reports existing warnings for feed links in index.md and the remote image used by configuration.md.
• No new build failures were introduced.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud