feat: Godot's gdscript and resources filetypes (#364)

Author: Arrow-x

data/plenary/filetypes/builtin.lua

@@ -26,6 +26,9 @@ return {
     ['ex'] = 'elixir',
     ['exs'] = 'elixir',
     ['erb'] = 'eruby',
+    ['tres'] = 'gdresource',
+    ['tscn'] = 'gdresource',
+    ['gd'] = 'gdscript',
     ['fnl'] = 'fennel',
     ['gql'] = 'graphql',
     ['graphql'] = 'graphql',