update workflow from yarn to pnpm

Author: iainnash

.github/workflows/build.yml

@@ -13,12 +13,12 @@ jobs:
       - name: Install Node.js
         uses: actions/setup-node@v3
         with:
-          node-version: 18
-          cache: "yarn"
+          node-version: 22
+          cache: "pnpm"
 
       - name: Install project dependencies
         shell: bash
-        run: yarn
+        run: pnpm install
 
       - name: Build 🏗️
         run: yarn build