Base: Add manual page for FlappyBug

Author: https://github.com/DavidLindbom
Commit: ef30e5832a
Pull-request: https://github.com/SerenityOS/serenity/pull/11772
Reviewed-by: https://github.com/Rummskartoffel
Reviewed-by: https://github.com/bgianfo ✅

Base/usr/share/man/man6/FlappyBug.md

@@ -0,0 +1,15 @@
+## Name
+
+Flappy Bug
+
+## Synopsis
+
+```**sh
+$ FlappyBug
+```
+
+## Description
+
+Flappy Bug is a SerenityOS themed version of the 2013 game Flappy Bird.
+
+The goal of the game is to survive with Buggie as long as possible by avoiding obstacles. Buggie automatically decends by gravity and to ascend by clicking any key. Press the escape key to give up.