implement LoRA / QLoRA (#46)

* implement LoRA / QLoRA

- example of using MLX to fine-tune an LLM with low rank adaptation (LoRA) for a target task
- see also https://arxiv.org/abs/2106.09685
- based on https://github.com/ml-explore/mlx-examples/tree/main/lora

* add some command line flags I found useful during use
- --quiet -- don't print decorator text, just the generated text
- --prompt @/tmp/file.txt -- load prompt from file

* user can specify path to model OR model identifier in huggingface

* update mlx-swift reference

Co-authored-by: Ashraful Islam <ashraful.meche@gmail.com>
Co-authored-by: JustinMeans <46542161+JustinMeans@users.noreply.github.com>

Libraries/LLM/README.md

@@ -1,4 +1,4 @@
-#  Llama
+#  LLM
 
 This is a port of several models from:
 
@@ -6,7 +6,7 @@ This is a port of several models from:
 
 using the Hugging Face swift transformers package to provide tokenization:
 
-https://github.com/huggingface/swift-transformers
+- https://github.com/huggingface/swift-transformers
 
 The [Models.swift](Models.swift) provides minor overrides and customization --
 if you require overrides for the tokenizer or prompt customizations they can be
@@ -30,3 +30,12 @@ Currently supported model types are:
 See [Configuration.swift](Configuration.swift) for more info.
 
 See [llm-tool](../../Tools/llm-tool)
+
+# LoRA
+
+[Lora.swift](Lora.swift) contains an implementation of LoRA based on this example:
+
+- https://github.com/ml-explore/mlx-examples/tree/main/lora
+
+See [llm-tool/LoraCommands.swift](../../Tools/llm-tool/LoraCommands.swift) for an example of a driver and
+[llm-tool](../../Tools/llm-tool) for examples of how to run it.