add github action to update pkgdown site

.github/workflows/call-build-pkgdown.yml

@@ -0,0 +1,15 @@
+# Checks that the pkgdown site builds for a repository.
+# this assumes pkgdown is already set up.
+name: call-build-pkgdown
+# on specifies the build triggers. See more info at https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows
+on:
+# this workflow runs on pushes to main or master or any time a new tag is pushed
+# it also runs everytime a pull request to main or master is opened.
+  push:
+    branches: [main, master]
+    tags: ['*']
+  pull_request:
+    branches: [main, master]
+jobs:
+  call-workflow:
+    uses: nmfs-fish-tools/ghactions4r/.github/workflows/build-pkgdown.yml@main