Add GitHub workflow and LuaCheck

.github/workflows/build.yml

@@ -0,0 +1,11 @@
+on: [push, pull_request]
+name: build
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - name: lint
+        uses: Roang-zero1/factorio-mod-luacheck@master
+        with:
+          luacheckrc_url: https://raw.githubusercontent.com/minetest-mods/item_drop/master/.luacheckrc

.luacheckrc

@@ -0,0 +1,19 @@
+unused_args = false
+allow_defined_top = true
+max_line_length = 999
+
+ignore = {
+    "name", "drops", "i",
+}
+
+globals = {
+    "minetest",
+}
+
+read_globals = {
+    string = {fields = {"split", "trim"}},
+    table = {fields = {"copy", "getn"}},
+
+    "vector", "ItemStack",
+    "dump",
+}