Add book deploy in CI.

Author: ehuss

.github/workflows/deploy-docs.yaml

@@ -0,0 +1,30 @@
+name: Deploy Docs
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  doc:
+    name: Documentation
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install mdbook
+        run: |
+          mkdir mdbook
+          curl -Lf https://github.com/rust-lang/mdBook/releases/download/v0.4.1/mdbook-v0.4.1-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=./mdbook
+          echo ::add-path::`pwd`/mdbook
+      - name: Build book
+        run: cd doc && mdbook build
+      - name: Deploy to GitHub
+        run: |
+          cd doc/book
+          git init
+          git config user.name "Deploy from CI"
+          git config user.email ""
+          git add . .nojekyll
+          git commit -m "Deploy $GITHUB_SHA to gh-pages"
+          git remote add origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/$GITHUB_REPOSITORY
+          git push --force --set-upstream origin master:gh-pages