Avoid GH action dependency errors by adding more setup

.github/workflows/publish-demo.yml

@@ -19,6 +19,25 @@ jobs:
       - name: "Check out repository"
         uses: actions/checkout@v3
 
+      # To render using knitr, we need a few more setup steps...
+      # If we didn't want the examples to use `engine: knitr`, we could
+      # skip a few of the setup steps.
+      - name: "Setup pandoc"
+        uses: r-lib/actions/setup-pandoc@v2
+
+      - name: "Setup R"
+        uses: r-lib/actions/setup-r@v2
+
+      - name: "Setup R dependencies for Quarto's knitr engine"
+        uses: r-lib/actions/setup-r-dependencies@v2
+        with:
+          packages:
+            any::knitr
+            any::rmarkdown
+            any::downlit
+            any::xml2
+
+      # Back to our regularly scheduled Quarto output
       - name: "Set up Quarto"
         uses: quarto-dev/quarto-actions/setup@v2