Add a .luacheckrc file

We'll look into running this on Travis in the future, but for now this
is a nice way to prevent any regressions.

.luacheckrc

@@ -0,0 +1,34 @@
+std = "max"
+
+ignore = {
+    -- Allow access to undefined globals or their fields. In the future we'll
+    -- define all of CC's globals within this file
+    '113', '143',
+
+    -- FIXME: Ignore unused arguments and loop variables
+    '212', '213',
+
+    -- Disable line is too long for now. It would be possible to clean
+    -- this up in the future.
+    '631',
+}
+
+-- Only run the linter on ROM and bios for now, as the treasure disks
+-- are largely unsupported.
+include_files = {
+    'src/main/resources/assets/computercraft/lua/rom',
+    'src/main/resources/assets/computercraft/lua/bios.lua'
+}
+
+files['src/main/resources/assets/computercraft/lua/bios.lua'] = {
+    -- Allow declaring and mutating globals
+    allow_defined_top = true,
+    ignore = { '112', '121', '122', '131', '142' },
+}
+
+files['src/main/resources/assets/computercraft/lua/rom/apis'] = {
+    -- APIs may define globals on the top level. We'll ignore unused globals,
+    -- as obviously they may be used outside that API.
+    allow_defined_top = true,
+    ignore = { '131' },
+}