ci: run unit tests on nodejs v16 as well as v20

.github/workflows/unit-tests.yml

@@ -17,6 +17,7 @@ jobs:
     strategy:
       matrix:
         runs-on: [ubuntu-latest, macos-latest, windows-latest]
+        node-version: [16.x, 20.x]
       fail-fast: false
 
     runs-on: ${{ matrix.runs-on }}
@@ -28,7 +29,7 @@ jobs:
     - name: Set Node.js version
       uses: actions/setup-node@v4
       with:
-        node-version-file: .nvmrc
+        node-version: ${{ matrix.node-version }}
 
     - name: npm install
       run: npm install