add luacheck actions

.github/workflows/main.yml

@@ -0,0 +1,19 @@
+# This is a basic workflow to help you get started with Actions
+
+name: luacheck
+
+# Controls when the action will run. 
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  workflow_dispatch:
+jobs:
+  luacheck:
+    runs-on: ubuntu-latest
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v2
+      - name: luacheck
+        uses: nebularg/actions-luacheck@v1.1.0