Modifies check for prayer during XP drop and readme

[hoheps]

Mirrors the change in https://github.com/runelite/runelite/commit/8972a6de25345082ce5748e4a31528ba8079381b where it checks for the server varbit to confirm whether the prayer was flicked.

[l2-]

Oops i messed up the git command but i'll keep the commits on master. Thanks