feat: update workspace paths and enhance gitignore

- Updated stablediffusion crate path from "../stable-diffusion-burn" to "./crates/stable-diffusion-burn" for proper workspace resolution
- Enhanced .gitignore to include generated model files (.mpk, .pt, .bin, .safetensors, .ckpt) and user_data directory
- Added Cargo.lock to gitignore with appropriate comment
- Reorganized IDE files section in gitignore for better clarity
- Added newline at end of file for proper formatting

crates/stable-diffusion-burn/burn-crates/burn-rl/README.md

@@ -0,0 +1,6 @@
+# Burn RL
+
+<!-- This crate should be used with [burn](https://github.com/tracel-ai/burn). -->
+
+<!-- [![Current Crates.io Version](https://img.shields.io/crates/v/burn-rl.svg)](https://crates.io/crates/burn-rl)
+[![license](https://shields.io/badge/license-MIT%2FApache--2.0-blue)](https://github.com/tracel-ai/burn-rl/blob/master/README.md) -->