element tree 组件自定义展开合并图标

有的时候应业务需求，需要改变element组件原有的样式

需要覆盖原有的样式 只需要复制下面代码片段覆盖原有样式就OK

<style lang="css">
.el-tree .el-tree-node__expand-icon.expanded {
transform: rotate(0deg);
}
.el-tree .el-icon-caret-right:before {
content: '\e7a0';
color: #0FDCDD;
font-size: 18px;
}
.el-tree .el-tree-node__expand-icon.expanded.el-icon-caret-right:before {
content: '\e7a2';
color: #0FDCDD;
font-size: 18px;
}
.el-tree .is-leaf.el-tree-node__expand-icon.el-icon-caret-right:before{
content: '';
}
</style>