add .luacheckrc and github workflow

.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 +1,23 @@
+unused_args = false
+max_line_length= 240
+redefined = false
+
+globals = {
+	"biome_lib"
+}
+
+read_globals = {
+	-- Stdlib
+	string = {fields = {"split"}},
+	table = {fields = {"copy", "getn"}},
+
+	-- Minetest
+	"vector", "ItemStack",
+	"dump", "minetest",
+	"VoxelManip", "VoxelArea",
+	"PerlinNoise",
+
+	-- mods
+	"default", "intllib"
+
+}