Add GitHub Actions workflow to build and deploy documentation

.github/workflows/docs.yml

@@ -0,0 +1,23 @@
+name: docs
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  docs:
+    name: Build and deploy documentation
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Install Doxygen
+        run: sudo apt-get install -y doxygen graphviz
+      - name: Build documentation
+        run: doxygen Doxyfile
+      - name: Deploy documentation
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./doc/html

README.org

@@ -1,5 +1,6 @@
 * ShaderTool
 
 [[https://github.com/dlozeve/ShaderTool/actions/workflows/build.yml][https://github.com/dlozeve/ShaderTool/actions/workflows/build.yml/badge.svg]]
+[[https://dlozeve.github.io/ShaderTool/][https://github.com/dlozeve/ShaderTool/actions/workflows/docs.yml/badge.svg]]
 
 Live tool for developing OpenGL shaders interactively.