install pnpm in github actions

Author: fuziontech

.github/workflows/docker-frontend.yaml

@@ -45,6 +45,9 @@ jobs:
           cache: "pnpm"
           cache-dependency-path: frontend/package-lock.json
 
+      - name: Install pnpm
+        run: npm i -g pnpm
+
       - name: Install dependencies
         run: pnpm i