调整组中所有具有正确类的按钮大小，使它们变为“大”。
<div class="btn-group @(12)"> <button class="btn btn-primary">苹果</button> <button class="btn btn-primary">三星</button> <button class="btn btn-primary">索尼</button> </div>
<div class="btn-group btn-group-lg"> <button class="btn btn-primary">苹果</button> <button class="btn btn-primary">三星</button> <button class="btn btn-primary">索尼</button> </div>