Re-document() + check & host docs from dev branch

.github/workflows/pkgdown.yaml

@@ -1,10 +1,13 @@
 # Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
 # Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
+#
+# Edits from above workflow: also check pkgdown for PRs to `dev` branch, and
+# update the documentation web site on pushes to `dev` branch.
 on:
   push:
-    branches: [main, master]
+    branches: [main, master, dev]
   pull_request:
-    branches: [main, master]
+    branches: [main, master, dev]
   release:
     types: [published]
   workflow_dispatch: