Implement simultaneous PR checks for Node.js v20, v24.

Copied from #2006.

.github/workflows/pr-checks.yml

@@ -20,6 +20,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        node-version: [20, 24]
     permissions:
       contents: read
       security-events: write # needed to upload ESLint results
@@ -36,7 +37,7 @@ jobs:
       - name: Set up Node.js
         uses: actions/setup-node@v5
         with:
-          node-version: 24
+          node-version: ${{ matrix.node-version }}
           cache: 'npm'
 
       - name: Set up Python
@@ -51,7 +52,12 @@ jobs:
           npm config set script-shell bash
           npm ci
 
-      - name: Verify compiled JS up to date
+      - name: Verify compiled JS up to date (Node.js 20)
+        if: matrix.node-version == 20
+        run: .github/workflows/script/check-js-20.sh
+
+      - name: Verify compiled JS up to date (Node.js 24)
+        if: matrix.node-version == 24
         run: .github/workflows/script/check-js.sh
 
       - name: Verify PR checks up to date
@@ -73,7 +79,7 @@ jobs:
 
       - name: Upload sarif
         uses: github/codeql-action/upload-sarif@v3
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-latest' && matrix.node-version == 24
         with:
           sarif_file: eslint.sarif
           category: eslint