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-no-std-tests/README.md

@@ -0,0 +1,29 @@
+The `burn-no-std-tests` contains integration tests aimed to check `no_std` compatibility of `burn`, `burn-core`, `burn-tensor` and `burn-ndarray` packages.
+
+Currently there is only a minimal test that checks if mnist model can be built with `no_std`. More tests should be added to check completeness.
+
+The continuous integration (CI) should build with additional targets:
+
+ * `wasm32-unknown-unknown` - WebAssembly
+ * `thumbv7m-none-eabi` - ARM Cortex-M3
+ * `thumbv6m-none-eabi` - ARM Cortex-M0+
+
+Shell commands to build and test the package:
+
+```sh
+
+# install the new targets if not installed previously
+rustup target add thumbv6m-none-eabi
+rustup target add thumbv7m-none-eabi
+rustup target add wasm32-unknown-unknown
+
+# build for various targets 
+cargo build # regular build
+cargo build --target thumbv7m-none-eabi
+cargo build --target wasm32-unknown-unknown
+RUSTFLAGS="--cfg portable_atomic_unsafe_assume_single_core" cargo build --target thumbv6m-none-eabi
+
+# test
+cargo test
+
+ ```