Add prettier ci workflow (#22)

.github/workflows/prettier.yml

@@ -0,0 +1,22 @@
+name: Prettier Lint
+
+on:
+  pull_request:
+    branches: [main]
+
+jobs:
+  prettier:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          # Make sure the actual branch is checked out when running on pull requests
+          ref: ${{ github.head_ref }}
+          # This is important to fetch the changes to the previous commit
+          fetch-depth: 0
+      - name: Prettify code
+        uses: creyD/[email protected]
+        with:
+          dry: True
+          prettier_options: '--check **/*.{js,html}'