add gh-pages deployment CI script - Fix #461

Author: WebFreak001

.github/workflows/deploy-pages.yml

@@ -0,0 +1,49 @@
+name: deploy-pages
+
+on:
+  push:
+    branches:
+      - deploy-pages
+      - master
+
+jobs:
+  main:
+    name: Deploy to ghpages
+
+    runs-on: ubuntu-latest
+
+    steps:
+        # Clone repo + submodules
+      - name: Checkout source repo
+        uses: actions/checkout@v3
+        with:
+          submodules: 'recursive'
+          path: main
+
+      - name: Checkout ghpages repo
+        uses: actions/checkout@v3
+        with:
+          submodules: 'recursive'
+          ref: gh-pages
+          path: gh-pages
+
+      - name: Install DMD
+        uses: dlang-community/setup-dlang@v1
+        with:
+          compiler: dmd-latest
+
+      - name: Build HTML
+        shell: bash
+        run: |
+          cd main
+          dub upgrade
+          dub build -b ddox -v
+          ./DGrammar/generate_html_from_libdparse.sh
+          cp ./DGrammar/grammar.html docs/grammar.html
+          cp -r docs/* ../gh-pages
+          cd ../gh-pages
+
+      - uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          branch: gh-pages
+          repository: gh-pages