Add amd gpu support

[Mahdi-CV]

Tested on AMD MI300X and successfully ran FLUX.1 training. Results and setup details are shared here.

Summary of changes:

• Added requirements-amd.txt to support AMD GPUs, as the default environment includes NVIDIA-specific packages (e.g., bitsandbytes, torchao) that require alternative installation or source builds on AMD.
• Updated the README with clear instructions for installing PyTorch and bitsandbytes for AMD ROCm environments.
• Fixed a minor typo in the documentation.

Let me know if you'd like me to test on any additional AMD hardware or update the docs further!

[dkspwndj]

I using AMD Radeon 7900xtx. So installed this and see this message. Not support Radeon cards? :) If official support is difficult, please give me a Colab Notebook that can be used as a Colab.