[Feature Request] More useful --init file

I propose the use of a more useful default init file, which also includes the website's URL (like [Task](https://taskfile.dev/) does), for example:

```justfile
# https://just.systems

[private]
@default:
just --list

```

It will then behave, after the user has added more recipes, like this:
```
$ just
Available recipes:
ramdisk # mounts a Ramdisk at /mnt/ramdisk
system-info # prints basic system info
```

Making the default recipe quiet and private makes it a lot cleaner, and the reasoning behind adding the URL is twofold:
- Existing users can more easily find the link to the documentation;
- New users that don't know what a "justfile" is, can open the link inside it and learn more.