Set up spell-checking action

.github/workflows/spelling.yml

@@ -0,0 +1,20 @@
+name: Spell checking
+on:
+  push:
+  schedule:
+    # * is a special character in YAML so you have to quote this string
+    - cron: '15 * * * *'
+
+jobs:
+  build:
+    name: Spell checking
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2.0.0
+      with:
+        fetch-depth: 5
+    - uses: check-spelling/check-spelling@0.0.16-alpha
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        bucket: .github/actions
+        project: spell-check