chore: Add installation of antora extensions to gh action.

Author: Nico-AP

.github/workflows/publish-docs.yml

@@ -18,6 +18,9 @@ jobs:
       - name: Install Antora
         run: npm i antora
 
+      - name: Install Antora Extensions
+        run: npm i @antora/lunr-extension
+
       - name: Generate Site
         run: npx antora docs/antora-playbook.yml