Add HTML generation in workflow

Author: lefessan

.github/workflows/ubuntu.yml

@@ -48,3 +48,16 @@ jobs:
           path: guide/PDFs/*.pdf
           if-no-files-found: error
           retention-days: 0
+
+      - name: Generate HTML
+        run: |
+          cd guide
+          make html
+
+      - name: Upload HTML
+        uses: actions/upload-artifact@v3.1.0
+        with:
+          name: gnucobol-docs-html
+          path: guide/HTML
+          if-no-files-found: error
+          retention-days: 0