docs: add autocomplete doc (#8320)

docs/examples/autocomplete/autocomplete-template.vue

@@ -0,0 +1,87 @@
+<template>
+  <el-autocomplete
+    v-model="state"
+    :fetch-suggestions="querySearch"
+    popper-class="my-autocomplete"
+    placeholder="Please input"
+    @select="handleSelect"
+  >
+    <template #suffix>
+      <el-icon class="el-input__icon" @click="handleIconClick">
+        <edit />
+      </el-icon>
+    </template>
+    <template #default="{ item }">
+      <div class="value">{{ item.value }}</div>
+      <span class="link">{{ item.link }}</span>
+    </template>
+  </el-autocomplete>
+</template>
+
+<script lang="ts" setup>
+import { onMounted, ref } from 'vue'
+import { Edit } from '@element-plus/icons-vue'
+
+interface LinkItem {
+  value: string
+  link: string
+}
+
+const state = ref('')
+const links = ref<LinkItem[]>([])
+
+const querySearch = (queryString: string, cb) => {
+  const results = queryString
+    ? links.value.filter(createFilter(queryString))
+    : links.value
+  // call callback function to return suggestion objects
+  cb(results)
+}
+const createFilter = (queryString) => {
+  return (restaurant) => {
+    return (
+      restaurant.value.toLowerCase().indexOf(queryString.toLowerCase()) === 0
+    )
+  }
+}
+const loadAll = () => {
+  return [
+    { value: 'vue', link: 'https://github.com/vuejs/vue' },
+    { value: 'element', link: 'https://github.com/ElemeFE/element' },
+    { value: 'cooking', link: 'https://github.com/ElemeFE/cooking' },
+    { value: 'mint-ui', link: 'https://github.com/ElemeFE/mint-ui' },
+    { value: 'vuex', link: 'https://github.com/vuejs/vuex' },
+    { value: 'vue-router', link: 'https://github.com/vuejs/vue-router' },
+    { value: 'babel', link: 'https://github.com/babel/babel' },
+  ]
+}
+const handleSelect = (item: LinkItem) => {
+  console.log(item)
+}
+
+const handleIconClick = (ev: Event) => {
+  console.log(ev)
+}
+
+onMounted(() => {
+  links.value = loadAll()
+})
+</script>
+
+<style>
+.my-autocomplete li {
+  line-height: normal;
+  padding: 7px;
+}
+.my-autocomplete li .name {
+  text-overflow: ellipsis;
+  overflow: hidden;
+}
+.my-autocomplete li .addr {
+  font-size: 12px;
+  color: #b4b4b4;
+}
+.my-autocomplete li .highlighted .addr {
+  color: #ddd;
+}
+</style>