Add docs for the Rust examples in the ulib documentation, covering:
- Rust demo programs (dynamic and static linking)
- Build instructions using both Makefile and cargo
- u-boot-sys crate structure and FFI bindings
- Building examples outside the U-Boot tree
This provides parallel documentation to the existing C examples, making
it possible to use either language with ulib.
Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
bc33a6a74d