ci: add cargo doc deployment to gh pages

.github/workflows/deploy-docs.yml

@@ -0,0 +1,31 @@
+name: Deploy Documentation
+
+on:
+    push:
+        branches:
+            - main
+
+jobs:
+    build:
+        runs-on: ubuntu-latest
+
+        steps:
+            - name: Checkout code
+              uses: actions/checkout@v2
+
+            - name: Set up Rust
+              uses: actions-rs/toolchain@v1
+              with:
+                  toolchain: stable
+
+            - name: Build Documentation
+              run: |
+                  cd ladderz
+                  cargo doc
+                  cd ..
+
+            - name: Deploy to GitHub Pages
+              uses: peaceiris/actions-gh-pages@v3
+              with:
+                  github_token: ${{ secrets.GITHUB_TOKEN }}
+                  publish_dir: ./ladderz/target/doc