Add GitHub workflow and luacheck (#545)

Add badge to README
Fix luacheck warnings
Remove node_ownership globals (and support)

technic/tools/flashlight.lua

@@ -99,7 +99,7 @@ minetest.register_globalstep(function(dtime)
 			if node and node.name == "air" then
 				minetest.set_node(rounded_pos, {name="technic:light"})
 			end
-			local node = minetest.get_node_or_nil(old_pos)
+			node = minetest.get_node_or_nil(old_pos)
 			if node and node.name == "technic:light" then
 				minetest.remove_node(old_pos)
 			end
@@ -118,6 +118,6 @@ minetest.register_node("technic:light", {
 	walkable = false,
 	buildable_to = true,
 	sunlight_propagates = true,
-	light_source = LIGHT_MAX,
+	light_source = minetest.LIGHT_MAX,
 	pointable = false,
 })