In-app notifications

[Nekidev]

In-app notifications will probably be better than system notifications for app-related things (not for things like new episode or chapter notifications). This could be done creating a global React context and a function to send the notifications and dismiss them automatically after x seconds (or not dismissing them) with an X button to manually dismiss them.

Also they may have buttons and/or progress bars, but this has to be analyzed a bit more because state handling with these things is not that easy (and sometimes remote state updating may not even update states visually). IDK if any state-handling library would be able to help with this (suggestions welcome).