webtoapp-wordpress
This WordPress plugin allows you to access the push notification features of webtoapp.design directly from your WordPress admin dashboard. You can manually send notifications (like from your webtoapp.design dashboard) and use the dropdown menu to make the notification open a specific page of your website when a user clicks it. Additionally you can attach images from your media library to the notification.
Another neat feature is automatically sending a push notification when you publish a new post (which was previously only possible through Zapier).
You can find the plugin in the WordPress plugin directory.
What even is webtoapp.design?
webtoapp.design allows you to convert your WordPress website into an app for Android and iOS. (Actually it works with any website, but I assume you are most interested in WordPress).