upgrade GitHub actions, pin Node.js version to 16 (#172)

Author: mohsinulhaq

.github/workflows/ci.yml

@@ -13,11 +13,11 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
-      - name: Use Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v2
+      - uses: actions/checkout@v4
+      - name: Use Node.js v16
+        uses: actions/setup-node@v4
         with:
-          node-version: ${{ matrix.node-version }}
+          node-version: 16
       - name: yarn install, build, and test
         run: |
           yarn --frozen-lockfile