add install helm plugin

Author: jsjoeio

.github/workflows/build.yaml

@@ -42,6 +42,10 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }} 
 
+      # TODO@jsjoeio - worth caching?
+      - name: Install helm kubeval plugin 
+        run: helm plugin install https://github.com/instrumenta/helm-kubeval
+
       - name: Fetch dependencies from cache
         id: cache-root-node-mods
         uses: actions/cache@v3