Create hassfest validation workflow

Add GitHub Actions workflow for hassfest validation.

Author: koosoli

custom_components/esphome_designer/.github/workflows/hassfest.yaml

@@ -0,0 +1,14 @@
+name: Validate with hassfest
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: "0 0 * * *"
+
+jobs:
+  validate:
+    runs-on: "ubuntu-latest"
+    steps:
+      - uses: "actions/checkout@v3"
+      - uses: home-assistant/actions/hassfest@master