Add a new item template for launchSettings.json

It would be great to have an item template to create a basic `launchSettings.json` file. For content I was thinking to have the following.

```
{
"$schema": "http://json.schemastore.org/launchsettings.json",
"profiles": {
"ConsoleApp11": {
"commandName": "Project"
}
}
}
```

For CLI users that want to customize the command args (and other options) it's hard to know how to create this file without a template. Having the `$schema` declaration in the file is helpful because many editors/IDEs should enable completions/validations/etc.

There is no rush on adding this item template.