微信小程序 如何引入外部字体库iconfont的图标

@font-face {
 font-family: 'iconfont'; /* project id 518032 */
 src: url('//at.alicdn.com/t/font_518032_t2q88z3jok8iwwmi.eot');
 src: url('//at.alicdn.com/t/font_518032_t2q88z3jok8iwwmi.eot?#iefix') format('embedded-opentype'),
 url('//at.alicdn.com/t/font_518032_t2q88z3jok8iwwmi.woff') format('woff'),
 url('//at.alicdn.com/t/font_518032_t2q88z3jok8iwwmi.ttf') format('truetype'),
 url('//at.alicdn.com/t/font_518032_t2q88z3jok8iwwmi.svg#iconfont') format('svg');
}
.iconfont {
 font-family:"iconfont" !important;
 font-size:60rpx;
 font-style:normal;
 -webkit-font-smoothing: antialiased;
 -moz-osx-font-smoothing: grayscale;
}
/*本项目使用的18个图标 */
.icon-zhiding:before{content: '\e739';}
.icon-zuojiantou:before{content: '\e736';}
.icon-youjiantou:before{content: '\e735';}
.icon-shangjiantou:before{content: '\e734';}
.icon-xiajiantou1:before{content: '\e733';}
.icon-xiajiantou:before{content: '\e6cc';}
.icon-gengduotianchong:before{content: '\e67f';}
.icon-erweima:before{content: '\e65f';}
.icon-fenleiorguangchangorqita:before{content: '\e64f';}
.icon-dibiao:before{content: '\e64d';}
.icon-bangzhu:before{content: '\e64a';}
.icon-xinfeng:before{content: '\e640';}
.icon-duihuaxinxi:before{content: '\e639';}
.icon-sousuo:before{content: '\e62f';}
.icon-shouye:before{content: '\e62d';}
.icon-shezhi:before{content: '\e62a';}
.icon-shanchu:before{content: '\e629';}
.icon-dianhua:before{content: '\e61b';}

<view>
 <icon class="iconfont icon-zhiding"></icon>
 <icon class="iconfont icon-zuojiantou"></icon>
 <icon class="iconfont icon-youjiantou"></icon>
 <icon class="iconfont icon-shangjiantou"></icon>
 <icon class="iconfont icon-xiajiantou1"></icon>
 <icon class="iconfont icon-xiajiantou"></icon>
</view>
<view>
 <icon class="iconfont icon-gengduotianchong"></icon>
 <icon class="iconfont icon-erweima"></icon>
 <icon class="iconfont icon-fenleiorguangchangorqita"></icon>
 <icon class="iconfont icon-dibiao"></icon>
 <icon class="iconfont icon-bangzhu"></icon>
 <icon class="iconfont icon-xinfeng"></icon>
</view>
<view>
 <icon class="iconfont icon-duihuaxinxi"></icon>
 <icon class="iconfont icon-sousuo"></icon>
 <icon class="iconfont icon-shouye"></icon>
 <icon class="iconfont icon-shezhi"></icon>
 <icon class="iconfont icon-shanchu"></icon>
 <icon class="iconfont icon-dianhua"></icon>
</view>