Add GitHub action to replace travis

.github/workflows/github-pages.yml

@@ -0,0 +1,19 @@
+name: GitHub pages
+on:
+  push:
+    branches:
+      - master
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+
+    - name: Build and deploy
+      uses: JamesIves/github-pages-deploy-action@2.0.0
+      env:
+        ACCESS_TOKEN: ${{ secrets.ACCESS_TOKEN }}
+        BRANCH: gh-pages
+        FOLDER: .vuepress/dist
+        BUILD_SCRIPT: yarn && yarn run build