add .luacheckrc and github workflow

.github/workflows/luacheck.yml

@@ -0,0 +1,17 @@
+name: luacheck
+
+on: [push, pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+    - 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 +1,27 @@
+
+unused = false
+max_line_length = 240
+
+globals = {
+	"drawers"
+}
+
+read_globals = {
+	-- Stdlib
+	string = {fields = {"split"}},
+	table = {fields = {"copy", "getn"}},
+
+	-- Minetest
+	"vector", "ItemStack",
+	"dump", "VoxelArea",
+
+	-- deps
+	"minetest",
+	"core",
+	"default",
+	"mcl_core",
+	"mcl_sounds",
+	"pipeworks",
+	"screwdriver",
+	"intllib"
+}