Added separate doxygen workflow

.github/workflows/doxygen.yml

@@ -0,0 +1,26 @@
+name: Doxygen
+
+on:
+  push:
+    branches: [ master ]
+  workflow_dispatch:
+
+jobs:
+  doxygen:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Doxygen
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y doxygen
+      - uses: actions/checkout@v2
+
+      - name: Generate docs
+        run: doxygen Doxyfile
+
+      - name: Deploy to GitHub Pages
+        uses: JamesIves/github-pages-deploy-action@releases/v3
+        with:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          BRANCH: gh-pages
+          FOLDER: docs/html