refactor example demo (#713)

* refactor: Adjust the example directory structure

* perf form demo

* refine editor-slide-upload css

* refine demo

src/views/example/components/Dropdown/SourceUrl.vue

@@ -0,0 +1,31 @@
+<template>
+  <el-dropdown :show-timeout="100" trigger="click">
+    <el-button plain>
+      外链
+      <i class="el-icon-caret-bottom el-icon--right"></i>
+    </el-button>
+    <el-dropdown-menu class="no-padding no-border" style="width:400px" slot="dropdown">
+      <el-form-item label-width="0px" style="margin-bottom: 0px" prop="source_uri">
+        <el-input placeholder="请输入内容" v-model="source_uri">
+          <template slot="prepend">填写url</template>
+        </el-input>
+      </el-form-item>
+    </el-dropdown-menu>
+  </el-dropdown>
+</template>
+
+<script>
+export default {
+  props: ['value'],
+  computed: {
+    source_uri: {
+      get() {
+        return this.value
+      },
+      set(val) {
+        this.$emit('input', val)
+      }
+    }
+  }
+}
+</script>