Add pnpm to test.yml

Author: michaelroudnitski

.github/workflows/test.yml

@@ -14,6 +14,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
+      - uses: pnpm/action-setup@v4
       - uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node_version }}