Fix Non-functional Project: Add Multi-source Pretrained Model and UVR5 Download, Enable , Colab Compatibility, and FastAPI Optimization

[XXXXRT666]

This PR addresses major issues rendering the project unusable and introduces several important enhancements:

install.sh:

• Added support for multiple download sources.
• Enabled optional download of the UVR5 model.

README:

• Fixed incorrect links to ensure correct navigation and setup guidance.

Colab Notebook:

• Updated to ensure it runs properly without errors, making the project usable from Colab.

Requirements:

• Added uvloop support to enhance FastAPI and Gradio performance on compatible platforms.