add luacheck

.github/workflows/luacheck.yml

@@ -0,0 +1,13 @@
+name: luacheck
+on: [push, pull_request]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: apt
+      run: sudo apt-get install -y luarocks
+    - name: luacheck install
+      run: luarocks install --local luacheck
+    - name: luacheck run
+      run: $HOME/.luarocks/bin/luacheck ./

.luacheckrc

@@ -0,0 +1,10 @@
+unused_args = false
+
+globals = {
+    "minetest",
+	"illumination",
+}
+
+read_globals = {
+	"vector",
+}

README.md

@@ -1,2 +1,5 @@
-# illumination
-Forked from https://notabug.org/Piezo_/minetest-illumination
+# Illumination [illumination]
+
+[![luacheck](https://github.com/pandorabox-io/illumination/workflows/luacheck/badge.svg)](https://github.com/pandorabox-io/illumination/actions)
+
+Improved fork of https://notabug.org/Piezo_/minetest-illumination