Extend neva new to be a builtin scaffolder

[emil14]

Problem

At the moment we have neva new command that creates new nevalang module on the disk. It looks like this:

neva new %path_to_module%

Generated module consist of only 2 files with a hello-world inside:

src/
  main.neva // <--- hello world
neva.yml    // <--- neva module manifest

It ain't much but it's an honest work but it saves you like about 1 minute of initializing the module manually. However, there are tools like yeoman, wasp, create-react-app, etc that allow to create custom templates for projects and scaffold them with cli.

Even though we don't have this problem, it sounds cool to have a builtin solution right inside official CLI tool.

Proposal

Any git-repo (or at least ones with neva.y(a)ml, we'll see) should be available as a template for neva new. Example: `neva new --template=github.com/emil14/neva-backend-layout" (let's imagine template contains boilerplate for databases, http middleware, JWT-auth, etc).

Implementation

It's not clear how exactly this should be implemented.

1. Figure out what's the MVP - smallest and simplest functionality
2. What's the template? Any repo? What are constraints?
3. Should we extend builder package? Reuse git-client code from there?

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Based on discussion with @Mr-Ao-Dragon and his PR #841

[emil14]

@Mr-Ao-Dragon I genuinely this is great idea and we should implement it :)

[Mr-Ao-Dragon]

yes!