[8.x] Add newLine() method to InteractsWithIO trait

[squatto]

When generating output in artisan commands and needing to output a blank line, I am constantly finding myself doing things like this:

$this->info('');
$this->info('Parsing CSV file');
$this->info('');

// or:

$this->info("\nParsing CSV file\n");

// or even worse:

$this->info(PHP_EOL . "Parsing CSV file" . PHP_EOL);

You can do it the "right" way by calling the newLine() method defined in the Symfony console StyleInterface:

$this->getOutput()->newLine();

That feel's a bit too verbose/heavy though. This PR simply makes the newLine() method directly accessible from the command itself:

$this->newLine();

Doing it this way ensures that the newline is output according to the current OutputStyle.

No tests are included in the PR because I wasn't able to find any existing tests that checked command output.

[squatto]

Given that this is a simple change that would most definitely be backward-compatible with 7.x, I'd be happy to submit a PR to that branch as well.

[driesvints]

@squatto 7.x isn't maintained anymore.