Add GitHub Action to build and deploy website

.github/workflows/ghpages.yml

@@ -0,0 +1,21 @@
+name: Build and deploy site to GitHub Pages
+on:
+  push:
+    branches:
+      - main
+jobs:
+  github-pages:
+    runs-on: ubuntu-16.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/cache@v1
+        with:
+          path: vendor/bundle
+          key: ${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-gems-
+      - uses: helaili/jekyll-action@2.0.1
+        env:
+          JEKYLL_PAT: ${{ secrets.JEKYLL_PAT }}
+        with:
+          jekyll_src: 'docs'