docs: show project layout in lis new and lis learn help

[ivov]

lis help new now includes a dir tree showing where the project lands, making it explicit that <name> becomes a new subdirectory of the current working directory.

lis new <name>

Create a new Lisette project in the current directory.

    .
    └── hello_world/
        ├── src/
        │   └── main.lis
        ├── lisette.toml
        ├── README.md
        ├── AGENTS.md
        └── .gitignore

Arguments:
    <name>    Name of the project, e.g. hello_world

lis help learn gets the same treatment.

Close #324

[github-actions]

Released in lisette-v0.2.1