chore: node version matrix in ci (#470)

Similar to open-feature/js-sdk-contrib#430

---------

Signed-off-by: Todd Baert <todd.baert@dynatrace.com>
Co-authored-by: Moritz Wiesinger <moritz.wiesinger@dynatrace.com>

.github/workflows/pr-checks.yaml

@@ -12,12 +12,19 @@ on:
 jobs:
   build-test-lint:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version:
+          - 16.x
+          - 18.x
+          - 20.x
 
     steps:
       - uses: actions/checkout@v3
-      - uses: actions/setup-node@v3
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v3
         with:
-          node-version: 16
+          node-version: ${{ matrix.node-version }}
           cache: 'npm'
 
       - name: Install
@@ -32,6 +39,19 @@ jobs:
       - name: Test
         run: npm run test
 
+  codecov-and-docs:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v3
+        with:
+          node-version: 16
+          cache: 'npm'
+
+      - name: Install
+        run: npm ci
+
       - name: Docs
         run: npm run docs