Swap from yarn@1 to npm

Author: Robert Jackson

.github/workflows/ci.yml

@@ -22,5 +22,5 @@ jobs:
       uses: actions/setup-node@v2
       with:
         node-version: ${{ matrix.node-version }}
-    - run: yarn install
-    - run: yarn test
+    - run: npm ci
+    - run: npm test