Add doc preview

.github/workflows/docs.yml

@@ -0,0 +1,89 @@
+name: Documentation
+
+on:
+  pull_request:
+    branches: [ main ]
+    paths:
+      - 'arbi/**'
+      - '.github/workflows/docs.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+  pull-requests: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  build-deploy-docs:
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Rust
+        run: |
+          rustup toolchain install nightly
+          rustup override set nightly
+      - name: Build static files (documentation)
+        run: |
+          RUSTDOCFLAGS="--html-in-header ./arbi/doc/header.html --cfg docsrs" cargo +nightly doc --no-deps --all-features
+      - name: Prepare PR-specific path
+        if: github.event_name == 'pull_request'
+        run: |
+          mkdir -p "pr-${{ github.event.number }}"
+          mv target/doc "pr-${{ github.event.number }}/doc"
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: '.'
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4
+      - name: Comment on PR - documentation preview link
+        uses: actions/github-script@v7
+        if: github.event_name == 'pull_request'
+        with:
+          script: |
+            const url = `${{ steps.deployment.outputs.page_url }}pr-${{ github.event.number }}/doc/arbi/index.html`;
+            const timestamp = new Date().toISOString();
+            const commit_hash = context.payload.pull_request.head.sha;
+            const message = `📚 Documentation preview: ${url}\n\n_Last updated: ${timestamp}_\n_Commit: ${commit_hash}_`;
+
+            // Look for an existing documentation preview comment.
+            const comments = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.payload.pull_request.number,
+            });
+            const doc_comment = comments.data.find(comment => 
+              comment.body.includes('📚 Documentation preview')
+            );
+
+            const comment_params = {
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                body: message
+            };
+
+            if (doc_comment) {
+              // If a comment exists, update the existing one.
+              await github.rest.issues.updateComment({
+                ...comment_params,
+                comment_id: doc_comment.id,
+              });
+            } else {
+              // If no comment exists, create a new one.
+              await github.rest.issues.createComment({
+                ...comment_params,
+                issue_number: context.payload.pull_request.number,
+              });
+            }