Build: update to GitHub Actions v5 to fix warnings, add Node.js 20

Fix GitHub Actions noise about "Node.js 20 actions are deprecated."
which is a pointless and confusing treadmill about internal primitives
like "checkout" and "setup-node" which are not simple shell scripts
but instead full containers that themselves utilize Node.js internally.
No user should have to care about this, and the warnings ideally either
would not exist, have a stable subset, or at the very least refer
to the action/v4 being deprecated instead of confusing details
about what those are internally made of.

Ref https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Author: Krinkle

.github/workflows/test.yml

@@ -11,26 +11,23 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node: [10, 12, 14]
+        node: [10, 12, 14, 20]
         os: [ubuntu-latest, windows-latest]
 
     steps:
       - name: Clone repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v5
 
       - name: Set Node.js version
-        uses: actions/setup-node@v1
+        uses: actions/setup-node@v5
         with:
           node-version: ${{ matrix.node }}
 
-      - run: node --version
       - run: npm --version
 
-      - name: Install npm dependencies
-        run: npm i
+      - run: npm install
 
-      - name: Run tests
-        run: npm test
+      - run: npm test
 
       # We test multiple Windows shells because of prior stdout buffering issues
       # filed against Grunt. https://github.com/joyent/node/issues/3584