feat: add command to generate a build file

Creates an initial `build.yaml` file based on the provided project name
and type.

Fixes #32

bin/build-configs

@@ -20,6 +20,27 @@ use Twig\Loader\FilesystemLoader;
 
 $app = new Application();
 
+$app->command(
+    'generate-build-file [-p|--project-name=] [-t|--type=]',
+    function(
+        string $projectName,
+        string $type,
+    ): void {
+        $projectName = str_replace('.', '-', $projectName);
+
+        // TODO: validate the project type.
+        $output = <<<EOF
+            name: $projectName
+            type: $type
+            EOF;
+
+        file_put_contents('build.yaml', $output);
+    }
+)->descriptions('Generate a new build.yaml file.', [
+    '--project-name' => 'The name of the project.',
+    '--type' => 'The project type.',
+]);;
+
 $app->command(
     'run [-c|--config-file=] [-o|--output-dir=]',
     function (
@@ -110,8 +131,6 @@ $app->command(
     '--output-dir' => 'The directory to create files in',
 ]);
 
-$app->setDefaultCommand('run');
-
 $app->run();
 
 /**