Add documentation page building workflow

.github/workflows/doc.yml

@@ -0,0 +1,29 @@
+name: Build Docs
+
+on: [push]
+
+jobs:
+  build:
+    name: Build docs
+    runs-on: ubuntu-latest
+    
+    steps:
+    - name: Setup Lua
+      uses: leafo/gh-actions-lua@v8
+      with:
+        luaVersion: 5.4
+
+    - name: Setup Lua Rocks
+      uses: leafo/gh-actions-luarocks@v4
+
+    - name: Setup dependencies
+      run: luarocks install --only-deps https://raw.githubusercontent.com/lunarmodules/LDoc/master/ldoc-scm-3.rockspec
+
+    - name: Checkout & build docs
+      run: git clone --branch=build_docs https://github.com/lunarmodules/LDoc.git ldoc && cd ldoc && chmod +x build_versioned_docs.sh && ./build_versioned_docs.sh
+
+    - name: Deploy
+      uses: peaceiris/actions-gh-pages@v3
+      with:
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        publish_dir: ldoc/doc_builds/