自己用的代码，特别推荐使用。以后可能搞成扩展☺
.fa::before { font-family: "Font Awesome 6 Free"; font-weight: 900; }
适用于 BBCode 警报：
.bbnotice::before, .bbsuccess::before, .bberror::before, .bbwarning::before { font-family: "Font Awesome 6 Free" !important; font-weight: 900 !important; }