build(test.yml): set node-version to 16

Author: gr2m

.github/workflows/test.yml

@@ -1,9 +1,10 @@
 name: Test
-on:
+"on":
   push: {}
   pull_request:
-    types: [opened, synchronize]
-
+    types:
+      - opened
+      - synchronize
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -12,5 +13,6 @@ jobs:
       - uses: actions/setup-node@v2
         with:
           cache: npm
+          node-version: 16
       - run: npm ci
       - run: npm test