Admin Dashboard Hello World Widget

Create a single-file WordPress plugin that registers an admin dashboard widget on the main wp-admin Dashboard screen (index.php). Use wp_dashboard_setup hook and wp_add_dashboard_widget with a unique widget ID. The widget title should be "Hello World" and the content should output a short welcome message like "Hello World!" plus one extra line like "This widget was added by Plugin0." Ensure proper capability check so only users who can manage_options see it (or at least edit_posts) and escape output with esc_html. Add a filter/action priority that ensures it loads normally. Include plugin header, ABSPATH guard, namespaced-like prefix functions (p0_hwdw_), and keep code minimal and production-safe.