Publish documentation when pushing to a tag (#156)

.github/workflows/doc.yml

@@ -0,0 +1,33 @@
+name: Documentation
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  doc:
+    name: Deploy documentation
+    runs-on: ubuntu-20.04
+
+    steps:
+
+    - name: Checkout the Git repository
+      uses: actions/checkout@v2
+
+    - name: Generate Documentation
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y cmake doxygen doxygen-latex graphviz
+        cd docs
+        sudo cmake .
+        doxygen Doxyfile.docs >/dev/null
+
+    - name: Deploy to GitHub Pages
+      uses: JamesIves/github-pages-deploy-action@v4.2.3
+      with:
+        branch: gh-pages
+        folder: docs/html
+        single-commit: true
+        clean: true
+        clean-exclude: CNAME