Test RSS diff in CI

.build.yml

@@ -24,6 +24,11 @@ tasks:
       echo 'cd davideisinger.com' >> ~/.buildenv
   - spelling: |
       npx cspell "content/**/*.md"
+  - rss: |
+      curl -s https://raw.githubusercontent.com/gohugoio/hugo/refs/tags/v$HUGO_VERSION/tpl/tplimpl/embedded/templates/_default/rss.xml \
+      | diff - ./themes/v2/layouts/_default/rss.xml \
+      | wc -l \
+      | grep 7
   - dither: |
       cd bin/dither
       sudo bundle install