Add llms subdir + update README (#145)

* add llms subdir + update README

* nits

* use same pre-commit as mlx

* update readmes a bit

* format

llms/qwen/convert.py

@@ -1,8 +1,9 @@
 import argparse
-from transformers import AutoModelForCausalLM
+import json
+
 import numpy as np
 import torch
-import json
+from transformers import AutoModelForCausalLM
 
 
 def replace_key(key: str) -> str:

llms/qwen/qwen.py

@@ -1,6 +1,7 @@
 import argparse
-from dataclasses import dataclass
 import json
+from dataclasses import dataclass
+
 import mlx.core as mx
 import mlx.nn as nn
 from mlx.utils import tree_unflatten