feat(vim): implement lua go to spec

This add a pattern for all lua files that will go to the corresponding
spec files. I don't think this will work on all the different projects
but, its a good start. There may need to be some tweaking to make it
work in vim plugins.

site-modules/core/files/vim/plugin/spec.lua

@@ -28,6 +28,10 @@ local alternates = {
     { type = alternate_type.SPEC, file = "spec/%1.spec.%2" },
     { type = alternate_type.SPEC, file = "tests/%1.spec.%2", default = true },
   },
+
+  ["(.*)%.lua$"] = {
+    { type = alternate_type.SPEC, file = "spec/%1_spec.lua", default = true },
+  },
 }
 
 local function file_exists(filename)