Switch to using pnpm

Author: slevithan

.github/workflows/main.yml

@@ -11,11 +11,14 @@ jobs:
       matrix:
         node-version:
           - 20
-          - 14
+          - 18
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
-      - run: npm install
-      - run: npm test
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 9
+      - run: pnpm install
+      - run: pnpm test