Adds app com.gacode.relaunchx

Add ReLaunchX app, which is a fork from ReLaunch hosted on F-Droid. The latter was abandoned by the author (as stated in README). Apart from that I have a new device on which I use the app but I cannot test/develop it on the original device so I decided to make a fork. App is used by community: https://www.mobileread.com/forums/showthread.php?t=284418