chore: fix pr workflow

Author: LGLabGreg

.github/workflows/pr.yml

@@ -19,6 +19,9 @@ jobs:
           node-version: '20.x'
           cache: 'pnpm'
 
+      - name: Install pnpm
+        run: npm install -g pnpm
+
       - name: Install dependencies
         run: pnpm install