feat: generate shell completion

[Eric-Song-Nop]

I saw clap_complete is in Cargo.toml, but did not see it's usage, so I created a simple completion subcommand with it. Feel free to remove it if it's redundant work.

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我看依赖里有clap_complete但是好像没有实现shell补全，就随便写了一个。假如其实已经有了就把这个issue 关了好了。

[Myriad-Dreamin]

Thanks. the clap_complete dependency was copied from other project. I also copied the generation code from the project just now.