add github workflow

.github/workflows/main.yml

@@ -0,0 +1,42 @@
+# Workflow from https://4comprehension.com/github-actions-reveal-js-and-automating-pdf-conversion/
+# using Decktape https://github.com/astefanutti/decktape
+# another option is https://github.com/bellbind/remarkjs-pdf
+name: Create-PDF
+
+# Controls when the workflow will run
+# Triggers the workflow on push or pull request events on any branch and when manually
+# triggered from the Actions tab
+on: [push, pull_request, workflow_dispatch]
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    name: Generate PDF
+    steps:
+      - name: Create "/presentations" directory
+        run: mkdir presentations && sudo chmod 777 presentations
+
+      - name: Get List of files
+        run: 
+          curl https://api.github.com/repos/${{ github.repository }}/contents?ref=main | grep \"name\" | grep \"*.html\", | cut -d \" -f4 > pagefiles.txt
+
+      - name:  Build pdfs   
+        run:  
+          for f in `cat pagefiles.txt`; do in="https://${{ github.repository_owner }}.github.io/${{ github.event.repository.name }}/${f}"; out="presentations/${f%.html}.pdf"; docker run --rm -t -v `pwd`:/slides -v ~:/home/user astefanutti/decktape $in $out; done
+
+      - name: Remove list of files
+        run:
+         rm pagefiles.txt
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./presentations
+          publish_branch: pdfs-from-html
+          keep_files: true