ci: redeploy the site when a release changes the version it displays

website/vite.config.ts reads the root Cargo.toml at build time and stamps it
into __APP_VERSION__, which the footer and the page chrome render. Pages only
fired on `website/**`, and a release touches Cargo.toml and CHANGELOG.md and
nothing else, so the site never rebuilt for one: the footer kept advertising the
previous version until somebody happened to edit the website for other reasons.
That it currently reads v18.0.0 is luck — a docs commit landed the day after the
release.

Cargo.toml is left out of the pull_request paths on purpose. A dependency bump
changes nothing the site renders, and it is the deploy that needs the trigger.

.github/workflows/pages.yml

@@ -1,9 +1,15 @@
 name: Pages
 
+# The site stamps its footer version out of the root Cargo.toml at build time
+# (website/vite.config.ts reads it into __APP_VERSION__), so a release that only
+# touches Cargo.toml has to redeploy or the footer keeps advertising the previous
+# version until someone happens to edit the site. Cargo.toml is deliberately not
+# in the pull_request paths: a dependency bump there changes nothing the site
+# renders, and the deploy is what needs the trigger.
 on:
   push:
     branches: [master]
-    paths: ['website/**', '.github/workflows/pages.yml']
+    paths: ['website/**', '.github/workflows/pages.yml', 'Cargo.toml']
   pull_request:
     branches: ['**']
     paths: ['website/**', '.github/workflows/pages.yml']