add mkdocs workflow

.github/workflows/mkdocs.yml

@@ -0,0 +1,24 @@
+name: Deploy
+on:
+  push:
+    branches:
+      - mkdocs
+jobs:
+  build:
+    name: Deploy docs to GitHub Pages
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Build
+        uses: Tiryoh/actions-mkdocs@v0
+        with:
+          mkdocs_version: 'latest' # option
+          #mkdocs_version: '1.1' # option
+          requirements: 'docs/requirements.txt' # option
+          configfile: 'mkdocs.yml' # option
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./site