feat(CLI): Add a demo command to give users a interactive shell and try envd

[gaocegege]

Description

envd demo creates a build.envd demo and up it.

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Message from the maintainers:

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[kemingy]

Can we support envd up -f <URL> to build and run the remote envd file?

[gaocegege]

SGTM but the build context is still a problem. We cannot get the remote build context from the URL.

[VoVAllen]

Probably we can make this part of envd init command, such as envd init --demo

[gaocegege]

In my opinion, the command envd demo should create the build.envd in tmp/xx/ then run envd up based on this. Then the users can get a shell from it directly.

[aseaday]

If it is just a creation of build.envd and up, I dont think we should provide a top-level subcommand for it. But I think we could do more and how about we provide a interfact shell like:

$ envd demo
> Which one do you want to use: Python/R/Julia
The following packages will be installed for you:
- numpy
- 
> What packages do you want install extra

[gaocegege]

Looks promising to me. :tada:

[gaocegege]

It also can be used in envd init

[aseaday]

It also can be used in envd init

yes, we could had a feature to support interactive set simple envd build manifest first.

[kemingy]

interactive shell:

• https://github.com/charmbracelet/gum

[AlexXi19]

This would be helpful, an interactive shell to choose a simple initial configuration.

[aseaday]

Should we promote this issue's priority? @gaocegege @VoVAllen @kemingy

[gaocegege]

I marked the issue priority/medium

[AlexXi19]

Interested in this issue, could use this library: https://github.com/charmbracelet/bubbletea

[gaocegege]

The lib LGTM. Please pick it up if you are interested in it!

[gaocegege]

/assign @AlexXi19