Improve the user experience to enable HAMi vgpu on Volcano

[william-wang]

Issue or feature description

As we know, vgpu feature consists of several parts such as HAMi core, volcano-vgpu-device-plugin and scheduler. How to coordinate these parts to help user to enable it easier is so important especially for latest enhancement like vgpu binpacking and spreading ability. This issue is used to track the vgpu feature doc optimizition.

• Add the Volcano installation step in Install and Uninstall part.
• Add examples or guide for user reference to enable HAMi and device sharing scheduler plugin in Volcano.

[william-wang]

@Monokaix please help to add the Volcano installation step in the readme.