This mod allows you to afk without fear of getting disconnected. It will make 4 attempts to reconnect you to the server you were disconnected from, with a delay of 3, 10, 60 and 300 seconds. After 4 failed attempts it will no longer try to reconnect.
(Btw you can exit the disconnect screen with Esc)
(Mod doesn't change the background or the font, I was using a resource pack when I took the screenshots)
This mod is available under the CC0 license. Feel free to learn from it and incorporate it in your own projects.