perf(layer): 新增 btnAlign 按钮布局

src/module/layer/index.vue

@@ -65,7 +65,7 @@
         @click="closeHandle"
       ></a
     ></span>
-    <div v-if="btn && btn.length > 0" class="layui-layer-btn">
+    <div v-if="btn && btn.length > 0" class="layui-layer-btn" :class="['layui-layer-btn-' + btnAlign]">
       <template v-for="(b, index) in btn" :key="index">
         <a :class="['layui-layer-btn' + index]" @click="b.callback">{{
           b.text
@@ -113,6 +113,7 @@ const props = withDefaults(
     shade?: boolean
     shadeClose?: boolean
     closeBtn?: boolean
+    btnAlign?: string
   }>(),
   {
     id: 'layer',
@@ -129,6 +130,7 @@ const props = withDefaults(
     shade: false,
     shadeClose: true,
     closeBtn: true,
+    btnAlign: 'l'
   }
 )