Greasemonkey文档
    violentmonkey文档

    TamperMonkey中有GM_addStyle方法，Greasemonkey没有这个方法，所以要做兼容

    为了兼容没有addStyle

    1. export function addStyle (styleContent) {
    2.   if (!styleContent) {
    3.     return
    4.   }
    5.   // eslint-disable-next-line
    6.   if (window.GM_addStyle) {
    7.     // eslint-disable-next-line
    8.     window.GM_addStyle(styleContent)
    9.   } else {
    10.     const style = document.createElement('style')
    11.     style.innerHTML = styleContent
    12.     const head = document.getElementsByTagName('head')[0]
    13.     head.appendChild(style)
    14.   }
    15. }