List of some oversights

Hello asrob,
Nice module ;-)
Maybe you can also add the file "package.json" and "config.js", for run "npm install" and after use gulp ! ...
https://www.drupal.org/docs/8/themes/zurb-foundation-user-guide/zurb-fou...

"logo.svg" can also be added to avoid console error of 404 (Not Found)
and "theme-settings.php"

I notice also you forgot the functions "file_get_contents" for all the files xxx.scss so the files are feeded with the path...
inside : src/Generators/SubthemeGenerator.php

    $scss_base_files = glob($zfPath . 'STARTER/scss/base/*.scss');
    foreach ($scss_base_files as $scss_base_file) {
      $this->addFile()
        ->path($prefix . 'scss/base/' . basename($scss_base_file))
        ->content($scss_base_file);
    }

    $scss_layout_files = glob($zfPath . 'STARTER/scss/layout/*.scss');
    foreach ($scss_layout_files as $scss_layout_file) {
      $this->addFile()
        ->path($prefix . 'scss/layout/' . basename($scss_layout_file))
        ->content($scss_layout_file);
    }

    $scss_modules_files = glob($zfPath . 'STARTER/scss/modules/*.scss');
    foreach ($scss_modules_files as $scss_modules_file) {
      $this->addFile()
        ->path($prefix . 'scss/modules/' . basename($scss_modules_file))
        ->content($scss_modules_file);
    }

    $scss_states_files = glob($zfPath . 'STARTER/scss/states/*.scss');
    foreach ($scss_states_files as $scss_states_file) {
      $this->addFile()
        ->path($prefix . 'scss/states/' . basename($scss_states_file))
        ->content($scss_states_file);
    }

    $scss_theme_files = glob($zfPath . 'STARTER/scss/theme/*.scss');
    foreach ($scss_theme_files as $scss_theme_file) {
      $this->addFile()
        ->path($prefix . 'scss/theme/' . basename($scss_theme_file))
        ->content($scss_theme_file);
    }

should be

    $scss_base_files = glob($zfPath . 'STARTER/scss/base/*.scss');
    foreach ($scss_base_files as $scss_base_file) {
      $this->addFile()
        ->path($prefix . 'scss/base/' . basename($scss_base_file))
        ->content(file_get_contents($scss_base_file));
    }

    $scss_layout_files = glob($zfPath . 'STARTER/scss/layout/*.scss');
    foreach ($scss_layout_files as $scss_layout_file) {
      $this->addFile()
        ->path($prefix . 'scss/layout/' . basename($scss_layout_file))
        ->content(file_get_contents($scss_layout_file));
    }

    $scss_modules_files = glob($zfPath . 'STARTER/scss/modules/*.scss');
    foreach ($scss_modules_files as $scss_modules_file) {
      $this->addFile()
        ->path($prefix . 'scss/modules/' . basename($scss_modules_file))
        ->content(file_get_contents($scss_modules_file));
    }

    $scss_states_files = glob($zfPath . 'STARTER/scss/states/*.scss');
    foreach ($scss_states_files as $scss_states_file) {
      $this->addFile()
        ->path($prefix . 'scss/states/' . basename($scss_states_file))
        ->content(file_get_contents($scss_states_file));
    }

    $scss_theme_files = glob($zfPath . 'STARTER/scss/theme/*.scss');
    foreach ($scss_theme_files as $scss_theme_file) {
      $this->addFile()
        ->path($prefix . 'scss/theme/' . basename($scss_theme_file))
        ->content(file_get_contents($scss_theme_file));
    }

the "file_get_contents" functions are also absent from all image files:

    $gif_files = glob($zfPath . 'STARTER/images/foundation/orbit/*.gif');
    foreach ($gif_files as $gif_file) {
      $this->addFile()
        ->path($prefix . 'images/foundation/orbit/' . basename($gif_file))
        ->content($gif_file);
    }

    $jpg_files = glob($zfPath . 'STARTER/images/foundation/orbit/*.jpg');
    foreach ($jpg_files as $jpg_file) {
      $this->addFile()
        ->path($prefix . 'images/foundation/orbit/' . basename($jpg_file))
        ->content($jpg_file);
    }

    $png_files = glob($zfPath . 'STARTER/images/foundation/orbit/*.png');
    foreach ($png_files as $png_file) {
      $this->addFile()
        ->path($prefix . 'images/foundation/orbit/' . basename($png_file))
        ->content($png_file);
    }

should be

    $gif_files = glob($zfPath . 'STARTER/images/foundation/orbit/*.gif');
    foreach ($gif_files as $gif_file) {
      $this->addFile()
        ->path($prefix . 'images/foundation/orbit/' . basename($gif_file))
        ->content(file_get_contents($gif_file));
    }

    $jpg_files = glob($zfPath . 'STARTER/images/foundation/orbit/*.jpg');
    foreach ($jpg_files as $jpg_file) {
      $this->addFile()
        ->path($prefix . 'images/foundation/orbit/' . basename($jpg_file))
        ->content(file_get_contents($jpg_file));
    }

    $png_files = glob($zfPath . 'STARTER/images/foundation/orbit/*.png');
    foreach ($png_files as $png_file) {
      $this->addFile()
        ->path($prefix . 'images/foundation/orbit/' . basename($png_file))
        ->content(file_get_contents($png_file));
    }