feat: add empty setup function

Will be used later to setup everything so that a language works properly
in each situation.

lua/nvim-treesitter.lua

@@ -0,0 +1,10 @@
+local api = vim.api
+
+local M = {}
+
+-- This function sets up everythin needed for a given language
+-- this is the main interface through the plugin
+function M.setup(lang)
+end
+
+return M