Add sitemap generation functionality and update dependencies

This pull request introduces the ability to generate a sitemap for the project. It includes the addition of a new file, GenerateSitemap.php, which contains a command class to generate the sitemap using the SitemapGenerator::create function. The generated sitemap is written to public/sitemap.xml, and the command provides status messages in the console. The schedule in src/app/Console/Kernel.php is modified to include a daily task for generating the sitemap. Additionally, the composer.json file is updated to include "spatie/laravel-sitemap": "^6.3" as a new dependency.