Add name/description to devbox init

[vhsantos]

What problem are you trying to solve?

When generating the documentation devbox generate readme some sections (name/description) on the Markdown are missing, because this fields don't exists on the devbox.json file, example:

Current:

<!-- gen-readme start - generated by https://github.com/jetify-com/devbox/ -->
## Getting Started

This project uses [devbox](https://github.com/jetify-com/devbox) to manage its development environment.

Install devbox:
====

Expected:

====
<!-- gen-readme start - generated by https://github.com/jetify-com/devbox/ -->

# My Project Name

It is always nice to have some description.

## Getting Started

This project uses [devbox](https://github.com/jetify-com/devbox) to manage its development environment.

Install devbox:
====

What solution would you like?

When running the command devbox init

Give the user some options/flags to allow passing or filling in the name/description.

$devbox init --name "My Project Name" --description "It is always nice to have some description."

or

$devbox init --interactive
Project Name: My Project Name
Project Description: It is always nice to have some description.
Devbox project created
$

Alternatives you've considered

No response