fix: don't install parser if it is already configured

lua/godotdev/tree-sitter.lua

@@ -1,3 +1,12 @@
+local parsers_ok, ts_parsers = pcall(require, "nvim-treesitter.parsers")
+if not parsers_ok then
+  return
+end
+
+if ts_parsers.has_parser('gdshader') then
+  return
+end
+
 local ok, ts_configs = pcall(require, "nvim-treesitter.configs")
 if not ok then
   return
@@ -17,14 +26,13 @@ vim.filetype.add({
   },
 })
 
-local parsers_ok, ts_parsers = pcall(require, "nvim-treesitter.parsers")
 if parsers_ok then
   local parser_configs = ts_parsers.get_parser_configs()
   parser_configs.gdshader = {
     used_by = { "gdshader" }, -- filetype
     install_info = {
-      url = "", -- no external parser
-      files = {}, -- no parser files
+      url = "",               -- no external parser
+      files = {},             -- no parser files
       generate_requires_npm = false,
       requires_generate_from_grammar = false,
     },