一直等待并执行回调函数
This script should not be not be installed directly. It is a library for other scripts to include with the meta directive // @require https://update.greasyfork.org/scripts/464516/1179152/WaitFor.js
一直等待并执行回调函数
使用：
WaitFor(()=>{return true}, ()=>{console.log(1)});
cond 条件回调函数，当cond()为真则执行callback
callback 回调函数
delay 多久检查一次条件，单位ms，默认100
