Add suggestion when not using workers (statamic#58)

src/Commands/StaticSiteGenerate.php

@@ -21,7 +21,7 @@ class StaticSiteGenerate extends Command
  *
  * @var string
  */
- protected $signature = 'statamic:ssg:generate {--workers=1}';
+ protected $signature = 'statamic:ssg:generate {--workers=}';
 
  /**
  * The console command description.
@@ -51,8 +51,12 @@ public function handle()
  {
  Partyline::bind($this);
 
+ if (! $workers = $this->option('workers')) {
+ $this->comment('You may be able to speed up site generation significantly by installing spatie/fork and using multiple workers (requires PHP 8+).');
+ }
+
  $this->generator
- ->workers($this->option('workers'))
+ ->workers($workers ?? 1)
  ->generate();
  }
 }