CI: dispatch a site rebuild on record changes

.github/workflows/dispatch-site.yaml

@@ -0,0 +1,33 @@
+name: Notify site
+
+# Validate everything on main, then tell the site repo to rebuild. Requires
+# the SITE_DISPATCH_TOKEN secret: a fine-grained PAT for the site repo with
+# "Contents: read and write" permission.
+on:
+  push:
+    branches: [main]
+    paths: ["records/**"]
+
+permissions:
+  contents: read
+
+jobs:
+  # Full-set validation of main's records — the dispatch only fires when the
+  # state the site will fetch is valid (PR validation is the first gate; this
+  # covers direct pushes and anything that slipped through).
+  validate:
+    uses: CGIAR-Climate-Data-Hub/cdh-metadata-standard/.github/workflows/validate-records.yaml@main
+    with:
+      path: records
+      changed-only: false
+      tooling-ref: v0.2.0
+
+  dispatch:
+    needs: validate
+    runs-on: ubuntu-latest
+    steps:
+      - uses: peter-evans/repository-dispatch@v4
+        with:
+          token: ${{ secrets.SITE_DISPATCH_TOKEN }}
+          repository: CGIAR-Climate-Data-Hub/climate-data-hub
+          event-type: records-updated