Add mdbook documentation for the sync server

.github/workflows/publish-docs.yml

@@ -0,0 +1,30 @@
+name: docs
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: write
+
+jobs:
+  mdbook-deploy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup mdBook
+        uses: peaceiris/actions-mdbook@v2
+        with:
+          # if this changes, change it in .github/workflows/checks.yml as well
+          mdbook-version: '0.4.48'
+
+      - run: mdbook build docs
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./docs/book