Use 16:9 aspect and bump reveal.js to 5.1.0

Change-Id: I6384639329daef18a40ca55cbd3c4eab0ae500e1
diff --git a/inst/reveal.js-5.1.0/.github/workflows/js.yml b/inst/reveal.js-5.1.0/.github/workflows/js.yml
new file mode 100644
index 0000000..071e030
--- /dev/null
+++ b/inst/reveal.js-5.1.0/.github/workflows/js.yml
@@ -0,0 +1,31 @@
+name: tests
+
+on:
+  - push
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version:
+          - 18
+          - 20
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+
+      - run: npm install
+      - run: npm run build --if-present
+      - run: npm test
+        env:
+          CI: true