FLUX: Add support for setup configuration to publish module

[madroidmaq]

Added the setup.py configuration file, supporting download and use via pip，It can be better disseminated and can also be better referenced in other projects for secondary creation.

• Change flux to mlx_flux
• Add setup.py config
• Update readme

@namin @angeloskath Let me know your opinions.

Usages：

pip install mlx_flux

Image Generation:

mlx_flux.generate --model schnell \
    --n-images 1 \
    --image-size 512x1024 \
    --verbose \
    'A photo of an astronaut riding a horse on Mars.'

or

mlx_flux.txt2image --model schnell \
    --n-images 1 \
    --image-size 512x1024 \
    --verbose \
    'A photo of an astronaut riding a horse on Mars.'